doc-guide: kernel-doc: add comment about formatting verification

Currently there is no automated checking for kernel-doc comments except
running 'kernel-doc -v -none <filename>'. Mention the possibility to run
kernel-doc to verify formatting of the comments in the kernel-doc guide.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/doc-guide/kernel-doc.rst

@@ -44,6 +44,17 @@ that somebody changing the code will also change the documentation. The
 overview kernel-doc comments may be placed anywhere at the top indentation
 level.
 
+Running the ``kernel-doc`` tool with increased verbosity and without actual
+output generation may be used to verify proper formatting of the
+documentation comments. For example::
+
+	scripts/kernel-doc -v -none drivers/foo/bar.c
+
+The documentation format is verified by the kernel build when it is
+requested to perform extra gcc checks::
+
+	make W=n
+
 Function documentation
 ----------------------