diff --git a/Buildscr b/Buildscr
index 24db5913..c143c9df 100644
--- a/Buildscr
+++ b/Buildscr
@@ -123,9 +123,9 @@ in putty do echo '$#define BINARY_VERSION $(Winvercommas)' >> version.h
 in putty do sed -i '/set(DEFAULT_COMMIT/s/unavailable/$(vcsfullid)/' cmake/gitcommit.cmake
 
 in . do mkdir docbuild
-in docbuild do cmake ../putty
-in docbuild do make -j$(nproc) VERBOSE=1 doc
-in putty/doc do cp ../../docbuild/doc/*.1 .
+in docbuild do cmake ../putty/doc
+in docbuild do make -j$(nproc) VERBOSE=1
+in putty/doc do cp ../../docbuild/*.1 .
 
 in putty do ./mksrcarc.sh
 in putty do ./mkunxarc.sh '$(Uxarcsuffix)'
@@ -198,10 +198,10 @@ ifneq "$(cross_winsigncode)" "" in putty/windows do $(cross_winsigncode) -N -i h
 in putty do for hash in md5 sha1 sha256 sha512; do for dir_plat in "build32 w32" "build64 w64" "abuild32 wa32" "abuild64 wa64"; do set -- $$dir_plat; (cd windows/$$1 && $${hash}sum *.exe | sed 's!\( \+\)!\1'$$2'/!;s!$$! (installer version)!') >> $${hash}sums.installer; done; done
 
 # Build a WiX MSI installer, for each build flavour.
-in putty/windows with wixonlinux do candle -arch x86 -dRealPlatform=x86 -dDllOk=yes -dBuilddir=build32/ -dWinver="$(Winver)" -dPuttytextver="$(Puttytextver)" -dHelpFilePath="../../docbuild/doc/putty.chm" installer.wxs && light -ext WixUIExtension -ext WixUtilExtension -sval installer.wixobj -o installer32.msi -spdb
-in putty/windows with wixonlinux do candle -arch x64 -dRealPlatform=x64 -dDllOk=yes -dBuilddir=build64/ -dWinver="$(Winver)" -dPuttytextver="$(Puttytextver)" -dHelpFilePath="../../docbuild/doc/putty.chm" installer.wxs && light -ext WixUIExtension -ext WixUtilExtension -sval installer.wixobj -o installer64.msi -spdb
-in putty/windows with wixonlinux do candle -arch x64 -dRealPlatform=Arm -dDllOk=no -dBuilddir=abuild32/ -dWinver="$(Winver)" -dPuttytextver="$(Puttytextver)" -dHelpFilePath="../../docbuild/doc/putty.chm" installer.wxs && light -ext WixUIExtension -ext WixUtilExtension -sval installer.wixobj -o installera32.msi -spdb
-in putty/windows with wixonlinux do candle -arch x64 -dRealPlatform=Arm64 -dDllOk=no -dBuilddir=abuild64/ -dWinver="$(Winver)" -dPuttytextver="$(Puttytextver)" -dHelpFilePath="../../docbuild/doc/putty.chm" installer.wxs && light -ext WixUIExtension -ext WixUtilExtension -sval installer.wixobj -o installera64.msi -spdb
+in putty/windows with wixonlinux do candle -arch x86 -dRealPlatform=x86 -dDllOk=yes -dBuilddir=build32/ -dWinver="$(Winver)" -dPuttytextver="$(Puttytextver)" -dHelpFilePath="../../docbuild/putty.chm" installer.wxs && light -ext WixUIExtension -ext WixUtilExtension -sval installer.wixobj -o installer32.msi -spdb
+in putty/windows with wixonlinux do candle -arch x64 -dRealPlatform=x64 -dDllOk=yes -dBuilddir=build64/ -dWinver="$(Winver)" -dPuttytextver="$(Puttytextver)" -dHelpFilePath="../../docbuild/putty.chm" installer.wxs && light -ext WixUIExtension -ext WixUtilExtension -sval installer.wixobj -o installer64.msi -spdb
+in putty/windows with wixonlinux do candle -arch x64 -dRealPlatform=Arm -dDllOk=no -dBuilddir=abuild32/ -dWinver="$(Winver)" -dPuttytextver="$(Puttytextver)" -dHelpFilePath="../../docbuild/putty.chm" installer.wxs && light -ext WixUIExtension -ext WixUtilExtension -sval installer.wixobj -o installera32.msi -spdb
+in putty/windows with wixonlinux do candle -arch x64 -dRealPlatform=Arm64 -dDllOk=no -dBuilddir=abuild64/ -dWinver="$(Winver)" -dPuttytextver="$(Puttytextver)" -dHelpFilePath="../../docbuild/putty.chm" installer.wxs && light -ext WixUIExtension -ext WixUtilExtension -sval installer.wixobj -o installera64.msi -spdb
 
 # Change the width field for our dialog background image so that it
 # doesn't stretch across the whole dialog. (WiX's default one does; we
@@ -223,13 +223,13 @@ ifneq "$(cross_winsigncode)" "" in putty/windows do $(cross_winsigncode) -i http
 
 # Build the standalone binaries, in both 32- and 64-bit flavours.
 # These differ from the previous set in that they embed the help file.
-in putty/windows/build32 with cmake_at_least_3.20 do cmake . -DPUTTY_EMBEDDED_CHM_FILE=$$(realpath ../../../docbuild/doc/putty.chm)
+in putty/windows/build32 with cmake_at_least_3.20 do cmake . -DPUTTY_EMBEDDED_CHM_FILE=$$(realpath ../../../docbuild/putty.chm)
 in putty/windows/build32 with cmake_at_least_3.20 do make -j$(nproc) VERBOSE=1
-in putty/windows/build64 with cmake_at_least_3.20 do cmake . -DPUTTY_EMBEDDED_CHM_FILE=$$(realpath ../../../docbuild/doc/putty.chm)
+in putty/windows/build64 with cmake_at_least_3.20 do cmake . -DPUTTY_EMBEDDED_CHM_FILE=$$(realpath ../../../docbuild/putty.chm)
 in putty/windows/build64 with cmake_at_least_3.20 do make -j$(nproc) VERBOSE=1
-in putty/windows/abuild32 with cmake_at_least_3.20 do cmake . -DPUTTY_EMBEDDED_CHM_FILE=$$(realpath ../../../docbuild/doc/putty.chm)
+in putty/windows/abuild32 with cmake_at_least_3.20 do cmake . -DPUTTY_EMBEDDED_CHM_FILE=$$(realpath ../../../docbuild/putty.chm)
 in putty/windows/abuild32 with cmake_at_least_3.20 do make -j$(nproc) VERBOSE=1
-in putty/windows/abuild64 with cmake_at_least_3.20 do cmake . -DPUTTY_EMBEDDED_CHM_FILE=$$(realpath ../../../docbuild/doc/putty.chm)
+in putty/windows/abuild64 with cmake_at_least_3.20 do cmake . -DPUTTY_EMBEDDED_CHM_FILE=$$(realpath ../../../docbuild/putty.chm)
 in putty/windows/abuild64 with cmake_at_least_3.20 do make -j$(nproc) VERBOSE=1
 
 # Build the 'old' binaries, which should still run on all 32-bit
@@ -257,12 +257,12 @@ in putty/windows do mkdir deliver
 in putty/windows do for subdir in build32 abuild32 build64 abuild64 buildold; do mkdir deliver/$$subdir; done
 in putty/windows do while read x; do mv $$x deliver/$$x; mv $$x.map deliver/$$x.map; done < to-sign.txt
 
-in putty/windows/deliver/buildold do zip -k -j putty.zip `ls *.exe | grep -v puttytel` ../../../docbuild/doc/putty.chm
-in putty/windows/deliver/build32 do zip -k -j putty.zip `ls *.exe | grep -v puttytel` ../../../docbuild/doc/putty.chm
-in putty/windows/deliver/build64 do zip -k -j putty.zip `ls *.exe | grep -v puttytel` ../../../docbuild/doc/putty.chm
-in putty/windows/deliver/abuild32 do zip -k -j putty.zip `ls *.exe | grep -v puttytel` ../../../docbuild/doc/putty.chm
-in putty/windows/deliver/abuild64 do zip -k -j putty.zip `ls *.exe | grep -v puttytel` ../../../docbuild/doc/putty.chm
-in docbuild/doc/html do zip puttydoc.zip *.html
+in putty/windows/deliver/buildold do zip -k -j putty.zip `ls *.exe | grep -v puttytel` ../../../docbuild/putty.chm
+in putty/windows/deliver/build32 do zip -k -j putty.zip `ls *.exe | grep -v puttytel` ../../../docbuild/putty.chm
+in putty/windows/deliver/build64 do zip -k -j putty.zip `ls *.exe | grep -v puttytel` ../../../docbuild/putty.chm
+in putty/windows/deliver/abuild32 do zip -k -j putty.zip `ls *.exe | grep -v puttytel` ../../../docbuild/putty.chm
+in putty/windows/deliver/abuild64 do zip -k -j putty.zip `ls *.exe | grep -v puttytel` ../../../docbuild/putty.chm
+in docbuild/html do zip puttydoc.zip *.html
 
 # Deliver the actual PuTTY release directory into a subdir `putty'.
 deliver putty/windows/deliver/buildold/*.exe putty/w32old/$@
@@ -279,10 +279,10 @@ deliver putty/windows/deliver/abuild32/*.exe putty/wa32/$@
 deliver putty/windows/deliver/abuild32/putty.zip putty/wa32/$@
 deliver putty/windows/deliver/abuild64/*.exe putty/wa64/$@
 deliver putty/windows/deliver/abuild64/putty.zip putty/wa64/$@
-deliver docbuild/doc/html/puttydoc.zip putty/$@
-deliver docbuild/doc/putty.chm putty/$@
-deliver docbuild/doc/puttydoc.txt putty/$@
-deliver docbuild/doc/html/*.html putty/htmldoc/$@
+deliver docbuild/html/puttydoc.zip putty/$@
+deliver docbuild/putty.chm putty/$@
+deliver docbuild/puttydoc.txt putty/$@
+deliver docbuild/html/*.html putty/htmldoc/$@
 deliver putty/putty-src.zip putty/$@
 deliver putty/*.tar.gz putty/$@
 
diff --git a/doc/CMakeLists.txt b/doc/CMakeLists.txt
index f7fcb4e2..eb273758 100644
--- a/doc/CMakeLists.txt
+++ b/doc/CMakeLists.txt
@@ -1,3 +1,13 @@
+cmake_minimum_required(VERSION 3.12)
+project(putty-documentation LANGUAGES)
+
+# This build script can be run standalone, or included as a
+# subdirectory of the main PuTTY cmake build system. If the latter, a
+# couple of things change: it has to set variables telling the rest of
+# the build system what manpages are available to be installed, and it
+# will change whether the 'make doc' target is included in 'make all'.
+
+include(FindGit)
 include(FindPerl)
 find_program(HALIBUT halibut)
 
@@ -23,9 +33,9 @@ if(HALIBUT AND PERL_EXECUTABLE)
         -DGIT_EXECUTABLE=${GIT_EXECUTABLE}
         -DOUTPUT_FILE=${INTERMEDIATE_VERSION_BUT}
         -DOUTPUT_TYPE=halibut
-        -P ${CMAKE_SOURCE_DIR}/cmake/gitcommit.cmake
-      DEPENDS ${CMAKE_SOURCE_DIR}/cmake/gitcommit.cmake
-      WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+        -P ${CMAKE_CURRENT_SOURCE_DIR}/../cmake/gitcommit.cmake
+      DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/../cmake/gitcommit.cmake
+      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/..
       COMMENT "Checking current git commit")
     add_custom_target(cmake_version_but
       BYPRODUCTS ${VERSION_BUT}
@@ -36,13 +46,13 @@ if(HALIBUT AND PERL_EXECUTABLE)
   endif()
 
   add_custom_command(OUTPUT copy.but
-    COMMAND ${PERL_EXECUTABLE} ${CMAKE_SOURCE_DIR}/licence.pl
+    COMMAND ${PERL_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/../licence.pl
       --copyrightdoc -o copy.but
-    DEPENDS ${CMAKE_SOURCE_DIR}/licence.pl ${CMAKE_SOURCE_DIR}/LICENCE)
+    DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/../licence.pl ${CMAKE_CURRENT_SOURCE_DIR}/../LICENCE)
   add_custom_command(OUTPUT licence.but
-    COMMAND ${PERL_EXECUTABLE} ${CMAKE_SOURCE_DIR}/licence.pl
+    COMMAND ${PERL_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/../licence.pl
       --licencedoc -o licence.but
-    DEPENDS ${CMAKE_SOURCE_DIR}/licence.pl ${CMAKE_SOURCE_DIR}/LICENCE)
+    DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/../licence.pl ${CMAKE_CURRENT_SOURCE_DIR}/../LICENCE)
 
   set(manual_sources
     ${CMAKE_CURRENT_BINARY_DIR}/copy.but
@@ -93,6 +103,14 @@ if(HALIBUT AND PERL_EXECUTABLE)
   list(APPEND doc_outputs puttydoc.txt)
 endif()
 
+macro(register_manpage title section)
+  list(APPEND manpage_outputs ${title}.${section})
+  if(NOT CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+    # Only set this variable if there _is_ a parent scope.
+    set(HAVE_MANPAGE_${title}_${section} ON PARENT_SCOPE)
+  endif()
+endmacro()
+
 macro(manpage title section)
   if(HALIBUT)
     add_custom_command(OUTPUT ${title}.${section}
@@ -101,15 +119,13 @@ macro(manpage title section)
         ${CMAKE_CURRENT_SOURCE_DIR}/man-${title}.but
       DEPENDS
         mancfg.but man-${title}.but)
-    list(APPEND manpage_outputs ${title}.${section})
-    set(HAVE_MANPAGE_${title}_${section} ON PARENT_SCOPE)
+    register_manpage(${title} ${section})
   elseif(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${title}.${section})
     add_custom_command(OUTPUT ${title}.${section}
       COMMAND ${CMAKE_COMMAND} -E copy_if_different
         ${CMAKE_CURRENT_SOURCE_DIR}/${title}.${section} ${title}.${section}
       DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/${title}.${section})
-    list(APPEND manpage_outputs ${title}.${section})
-    set(HAVE_MANPAGE_${title}_${section} ON PARENT_SCOPE)
+    register_manpage(${title} ${section})
   endif()
 endmacro()
 
@@ -124,7 +140,17 @@ manpage(pageant 1)
 manpage(psocks 1)
 manpage(psusan 1)
 
-add_custom_target(manpages ALL
-  DEPENDS ${manpage_outputs})
-add_custom_target(doc
-  DEPENDS ${doc_outputs} manpages)
+add_custom_target(manpages ALL DEPENDS ${manpage_outputs})
+add_custom_target(doc DEPENDS ${doc_outputs} manpages)
+
+if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+  # If we're doing a cmake from just the doc subdir, we expect the
+  # user to want to make all the documentation, including HTML and so
+  # forth. (What else would be the point?)
+  #
+  # But if we're included from the main makefile, then by default we
+  # only make the man pages (which are necessary for 'make install'),
+  # and we leave everything else to a separate 'make doc' target which
+  # the user can invoke if they need to.
+  add_custom_target(doc-default ALL DEPENDS doc)
+endif()