docs: Kbuild/Makefile: allow check for missing docs at build time

While this doesn't make sense for production Kernels, in order to
avoid regressions when documents are touched, let's add a
check target at the make file.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/Kconfig b/Documentation/Kconfig
new file mode 100644
index 0000000..66046fa
--- /dev/null
+++ b/Documentation/Kconfig
@@ -0,0 +1,13 @@
+config WARN_MISSING_DOCUMENTS
+
+	bool "Warn if there's a missing documentation file"
+	depends on COMPILE_TEST
+	help
+	   It is not uncommon that a document gets renamed.
+	   This option makes the Kernel to check for missing dependencies,
+	   warning when something is missing. Works only if the Kernel
+	   is built from a git tree.
+
+	   If unsure, select 'N'.
+
+
diff --git a/Documentation/Makefile b/Documentation/Makefile
index 2df0789..e145e4d 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -4,6 +4,11 @@
 
 subdir-y := devicetree/bindings/
 
+# Check for broken documentation file references
+ifeq ($(CONFIG_WARN_MISSING_DOCUMENTS),y)
+$(shell $(srctree)/scripts/documentation-file-ref-check --warn)
+endif
+
 # You can set these variables from the command line.
 SPHINXBUILD   = sphinx-build
 SPHINXOPTS    =