Documentation: stable: clarify patch series prerequisites

Add some clarifications for patches that have dependencies within the
patch series.

Signed-off-by: Hugo Villeneuve <[e-mail]>
Rule: add
Link: https://lore.kernel.org/stable/20230911203628.20068-1-hugo%40hugovil.com
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/process/stable-kernel-rules.rst

···
      git cherry-pick fd21073
      git cherry-pick <this commit>
 
+   Note that for a patch series, you do not have to list as prerequisites the
+   patches present in the series itself. For example, if you have the following
+   patch series:
+
+   .. code-block:: none
+
+     patch1
+     patch2
+
+   where patch2 depends on patch1, you do not have to list patch1 as
+   prerequisite of patch2 if you have already marked patch1 for stable
+   inclusion.
+
  * For patches that may have kernel version prerequisites specify them using
    the following format in the sign-off area: