Index: llvm/cmake/modules/AddSphinxTarget.cmake
===================================================================
--- llvm/cmake/modules/AddSphinxTarget.cmake
+++ llvm/cmake/modules/AddSphinxTarget.cmake
@@ -18,7 +18,7 @@
 #
 # ``project`` should be the project name
 function (add_sphinx_target builder project)
-  cmake_parse_arguments(ARG "" "SOURCE_DIR" "" ${ARGN})
+  cmake_parse_arguments(ARG "" "SOURCE_DIR;CONF_FILE_DIR" "" ${ARGN})
   set(SPHINX_BUILD_DIR "${CMAKE_CURRENT_BINARY_DIR}/${builder}")
   set(SPHINX_DOC_TREE_DIR "${CMAKE_CURRENT_BINARY_DIR}/_doctrees-${project}-${builder}")
   set(SPHINX_TARGET_NAME docs-${project}-${builder})
@@ -33,9 +33,14 @@
     set(ARG_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
   endif()
 
+  if (NOT ARG_CONF_FILE_DIR)
+    set(ARG_CONF_FILE_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
+  endif()
+
   add_custom_target(${SPHINX_TARGET_NAME}
                     COMMAND ${SPHINX_EXECUTABLE}
                             -b ${builder}
+                            -c ${ARG_CONF_FILE_DIR}
                             -d "${SPHINX_DOC_TREE_DIR}"
                             -q # Quiet: no output other than errors and warnings.
                             -t builder-${builder} # tag for builder