docs: submitting-patches: document the format for affiliation

Adding company name in round brackets to From/SoB lines
is fairly common, but I don't see it documented anywhere.
Every now and then people try to add the sponsorship lines
to the commit message, fun example from this merge window:

  Sponsored by:   The FreeBSD Foundation

from commit 2ce67f8bf1 ("wifi: iwlwifi: mvm: fix iwl_ssid_exist()
check"). Better format would be:

  Author: Miri Korenblit (FreeBSD Foundation) <...

Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Documentation/process/submitting-patches.rst

@@ -717,6 +717,12 @@ patch in the permanent changelog.  If the ``from`` line is missing,
 then the ``From:`` line from the email header will be used to determine
 the patch author in the changelog.
 
+The author may indicate their affiliation or the sponsor of the work
+by adding the name of an organization to the ``from`` and ``SoB`` lines,
+e.g.:
+
+	From: Patch Author (Company) <[email protected]>
+
 Explanation Body
 ^^^^^^^^^^^^^^^^