dim: Caution more against topic branches

They're very often just beaurocratic paperwork pushing because
maintainers refuse to give acks for merging patches through a single
tree. I guess the snarky intro wasn't clear enough, so elaborate.

Given that we don't even talk about topic branches anywhere else in
the docs hopefully this makes things a bit clearer.

v2: Fix typo (Maarten)

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

dim.rst

@@ -475,9 +475,13 @@ EXAMPLES
 
 Cross-subsystem topic branches
 ------------------------------
-So you want to send a pull request to another subsystem? Maintainers will likely
-get cranky if you ask them to pull a swath of unrelated drm patches, so we'll
-use a topic branch based upon Linus' tree with only the relevant patches.
+So you want to send a pull request to another subsystem? First, you don't want,
+it's much simpler to get Acks for merging through a single tree and then maybe
+later on backmerge. But if it cannot be avoided, read on.
+
+Maintainers will likely get cranky if you ask them to pull a swath of unrelated
+drm patches, so we'll use a topic branch based upon Linus' tree with only the
+relevant patches.
 
 First select a suitable *baseline* for your topic branch. For topic
 branches shared within the gpu/drm subsystem, base it on the latest