drm/doc: Add todo about connector_list_iter

At least radeon, amdgpu and nouveau should be converted. We have
patches for i915 already.

v2: Spelling (Sean).
Reviewed-by: NSean Paul <seanpaul@chromium.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170308141257.12119-2-daniel.vetter@ffwll.ch

Documentation/gpu/todo.rst

@@ -153,6 +153,19 @@ following drivers still use ``struct_mutex``: ``msm``, ``omapdrm`` and
 
 Contact: Daniel Vetter
 
+Switch to drm_connector_list_iter for any connector_list walking
+----------------------------------------------------------------
+
+Connectors can be hotplugged, and we now have a special list of helpers to walk
+the connector_list in a race-free fashion, without incurring deadlocks on
+mutexes and other fun stuff.
+
+Unfortunately most drivers are not converted yet. At least all those supporting
+DP MST hotplug should be converted, since for those drivers the difference
+matters. See drm_for_each_connector_iter() vs. drm_for_each_connector().
+
+Contact: Daniel Vetter
+
 Core refactorings
 =================