Documentation/process: mention patch changelog in review process

Extend the "Respond to review comments" section of "Submitting patches"
with reference to patch changelogs.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/process/submitting-patches.rst

@@ -318,7 +318,10 @@ understands what is going on.
 Be sure to tell the reviewers what changes you are making and to thank them
 for their time.  Code review is a tiring and time-consuming process, and
 reviewers sometimes get grumpy.  Even in that case, though, respond
-politely and address the problems they have pointed out.
+politely and address the problems they have pointed out.  When sending a next
+version, add a ``patch changelog`` to the cover letter or to individual patches
+explaining difference aganst previous submission (see
+:ref:`the_canonical_patch_format`).
 
 See Documentation/process/email-clients.rst for recommendations on email
 clients and mailing list etiquette.