+If you are a subsystem or branch maintainer, sometimes you need to slightly
+modify patches you receive in order to merge them, because the code is not
+exactly the same in your tree and the submitters'. If you stick strictly to
+rule (c), you should ask the submitter to rediff, but this is a totally
+counter-productive waste of time and energy. Rule (b) allows you to adjust
+the code, but then it is very impolite to change one submitter's code and
+make him endorse your bugs. To solve this problem, it is recommended that
+you add a line between the last Signed-off-by header and yours, indicating
+the nature of your changes. While there is nothing mandatory about this, it
+seems like prepending the description with your mail and/or name, all
+enclosed in square brackets, is noticeable enough to make it obvious that
+you are responsible for last-minute changes. Example :
+
+ Signed-off-by: Random J Developer <random@developer.example.org>
+ [lucky@maintainer.example.org: struct foo moved from foo.c to foo.h]
+ Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org>
+
+This practise is particularly helpful if you maintain a stable branch and
+want at the same time to credit the author, track changes, merge the fix,
+and protect the submitter from complaints. Note that under no circumstances
+can you change the author's identity (the From header), as it is the one
+which appears in the changelog.
+
+Special note to back-porters: It seems to be a common and useful practise
+to insert an indication of the origin of a patch at the top of the commit
+message (just after the subject line) to facilitate tracking. For instance,
+here's what we see in 2.6-stable :
+
+ Date: Tue May 13 19:10:30 2008 +0000
+
+ SCSI: libiscsi regression in 2.6.25: fix nop timer handling
+
+ commit 4cf1043593db6a337f10e006c23c69e5fc93e722 upstream
+
+And here's what appears in 2.4 :
+
+ Date: Tue May 13 22:12:27 2008 +0200
+
+ wireless, airo: waitbusy() won't delay
+
+ [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a]
+
+Whatever the format, this information provides a valuable help to people
+tracking your trees, and to people trying to trouble-shoot bugs in your
+tree.
+
+
+13) When to use Acked-by: and Cc:
+
+The Signed-off-by: tag indicates that the signer was involved in the
+development of the patch, or that he/she was in the patch's delivery path.
+
+If a person was not directly involved in the preparation or handling of a
+patch but wishes to signify and record their approval of it then they can
+arrange to have an Acked-by: line added to the patch's changelog.
+
+Acked-by: is often used by the maintainer of the affected code when that
+maintainer neither contributed to nor forwarded the patch.
+
+Acked-by: is not as formal as Signed-off-by:. It is a record that the acker
+has at least reviewed the patch and has indicated acceptance. Hence patch
+mergers will sometimes manually convert an acker's "yep, looks good to me"
+into an Acked-by:.
+
+Acked-by: does not necessarily indicate acknowledgement of the entire patch.
+For example, if a patch affects multiple subsystems and has an Acked-by: from
+one subsystem maintainer then this usually indicates acknowledgement of just
+the part which affects that maintainer's code. Judgement should be used here.
+When in doubt people should refer to the original discussion in the mailing
+list archives.