docs: clarify rules wrt tagging other people

Point out that explicit permission is usually needed to tag other people
in changes, but mention that implicit permission can be sufficient in
certain cases. This fixes slight inconsistencies between Reported-by:
and Suggested-by: and makes the usage more intuitive.

While at it, explicitly mention the dangers of our bugzilla instance, as
it makes it easy to forget that email addresses visible there are only
shown to logged-in users.

The latter is not a theoretical issue, as one maintainer mentioned that
his employer received a EU GDPR (general data protection regulation)
complaint after exposing a email address used in bugzilla through a tag
in a patch description.

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Simona Vetter <simona.vetter@ffwll.ch>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Thorsten Leemhuis <linux@leemhuis.info>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/588cf2763baa8fea1f4825f4eaa7023fe88bb6c1.1738852082.git.linux@leemhuis.info

Author: knurd

Documentation/process/5.Posting.rst

@@ -268,10 +268,15 @@ The tags in common use are:
  - Cc: the named person received a copy of the patch and had the
    opportunity to comment on it.
 
-Be careful in the addition of tags to your patches, as only Cc: is appropriate
-for addition without the explicit permission of the person named; using
-Reported-by: is fine most of the time as well, but ask for permission if
-the bug was reported in private.
+Be careful in the addition of the aforementioned tags to your patches, as all
+except for Cc:, Reported-by:, and Suggested-by: need explicit permission of the
+person named. For those three implicit permission is sufficient if the person
+contributed to the Linux kernel using that name and email address according
+to the lore archives or the commit history -- and in case of Reported-by:
+and Suggested-by: did the reporting or suggestion in public. Note,
+bugzilla.kernel.org is a public place in this sense, but email addresses
+used there are private; so do not expose them in tags, unless the person
+used them in earlier contributions.
 
 
 Sending the patch

Documentation/process/submitting-patches.rst

@@ -495,10 +495,10 @@ list archives.  A "# Suffix" may also be used in this case to clarify.
 
 If a person has had the opportunity to comment on a patch, but has not
 provided such comments, you may optionally add a ``Cc:`` tag to the patch.
-This is the only tag which might be added without an explicit action by the
-person it names - but it should indicate that this person was copied on the
-patch.  This tag documents that potentially interested parties
-have been included in the discussion.
+This tag documents that potentially interested parties have been included in
+the discussion. Note, this is one of only three tags you might be able to use
+without explicit permission of the person named (see 'Tagging people requires
+permission' below for details).
 
 Co-developed-by: states that the patch was co-created by multiple developers;
 it is used to give attribution to co-authors (in addition to the author
@@ -544,9 +544,9 @@ hopefully inspires them to help us again in the future. The tag is intended for
 bugs; please do not use it to credit feature requests. The tag should be
 followed by a Closes: tag pointing to the report, unless the report is not
 available on the web. The Link: tag can be used instead of Closes: if the patch
-fixes a part of the issue(s) being reported. Please note that if the bug was
-reported in private, then ask for permission first before using the Reported-by
-tag.
+fixes a part of the issue(s) being reported. Note, the Reported-by tag is one
+of only three tags you might be able to use without explicit permission of the
+person named (see 'Tagging people requires permission' below for details).
 
 A Tested-by: tag indicates that the patch has been successfully tested (in
 some environment) by the person named.  This tag informs maintainers that
@@ -596,11 +596,11 @@ Usually removal of someone's Tested-by or Reviewed-by tags should be mentioned
 in the patch changelog (after the '---' separator).
 
 A Suggested-by: tag indicates that the patch idea is suggested by the person
-named and ensures credit to the person for the idea. Please note that this
-tag should not be added without the reporter's permission, especially if the
-idea was not posted in a public forum. That said, if we diligently credit our
-idea reporters, they will, hopefully, be inspired to help us again in the
-future.
+named and ensures credit to the person for the idea: if we diligently credit
+our idea reporters, they will, hopefully, be inspired to help us again in the
+future. Note, this is one of only three tags you might be able to use without
+explicit permission of the person named (see 'Tagging people requires
+permission' below for details).
 
 A Fixes: tag indicates that the patch fixes an issue in a previous commit. It
 is used to make it easy to determine where a bug originated, which can help
@@ -618,6 +618,21 @@ Finally, while providing tags is welcome and typically very appreciated, please
 note that signers (i.e. submitters and maintainers) may use their discretion in
 applying offered tags.
 
+.. _tagging_people:
+
+Tagging people requires permission
+----------------------------------
+
+Be careful in the addition of the aforementioned tags to your patches, as all
+except for Cc:, Reported-by:, and Suggested-by: need explicit permission of the
+person named. For those three implicit permission is sufficient if the person
+contributed to the Linux kernel using that name and email address according
+to the lore archives or the commit history -- and in case of Reported-by:
+and Suggested-by: did the reporting or suggestion in public. Note,
+bugzilla.kernel.org is a public place in this sense, but email addresses
+used there are private; so do not expose them in tags, unless the person
+used them in earlier contributions.
+
 .. _the_canonical_patch_format:
 
 The canonical patch format