docs: dt: submitting-patches: Document sending DTS patches

Document two rules already widely used and enforced by DT maintainers
and SoC platform maintainers:

1. DTS patches should be placed at the end of driver patchset to
   indicate no dependencies of driver code on DTS.

2. DTS patches should be applied via SoC platform maintainers, because
   it is a driver-independent hardware description.  However some
   driver maintainers are reluctant to pick up portions of patchsets and
   prefer to take entire set at once.  For such cases, the DTS portion
   should be split into separate patchset, so it will not end up in the
   driver subsystem integration tree.

Signed-off-by: Krzysztof Kozlowski <[email protected]>
Reviewed-by: Laurent Pinchart <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Rob Herring (Arm) <[email protected]>

Author: krzk

Documentation/devicetree/bindings/submitting-patches.rst

@@ -54,11 +54,22 @@ I. For patch submitters
      followed as of commit bff5da4335256513497cc8c79f9a9d1665e09864
      ("checkpatch: add DT compatible string documentation checks"). ]
 
-  7) If a documented compatible string is not yet matched by the
+  7) DTS is treated in general as driver-independent hardware description, thus
+     any DTS patches, regardless whether using existing or new bindings, should
+     be placed at the end of patchset to indicate no dependency of drivers on
+     the DTS.  DTS will be anyway applied through separate tree or branch, so
+     different order would indicate the serie is non-bisectable.
+
+     If a driver subsystem maintainer prefers to apply entire set, instead of
+     their relevant portion of patchset, please split the DTS patches into
+     separate patchset with a reference in changelog or cover letter to the
+     bindings submission on the mailing list.
+
+  8) If a documented compatible string is not yet matched by the
      driver, the documentation should also include a compatible
      string that is matched by the driver.
 
-  8) Bindings are actively used by multiple projects other than the Linux
+  9) Bindings are actively used by multiple projects other than the Linux
      Kernel, extra care and consideration may need to be taken when making changes
      to existing bindings.
 
@@ -79,6 +90,10 @@ II. For kernel maintainers
   3) For a series going though multiple trees, the binding patch should be
      kept with the driver using the binding.
 
+  4) The DTS files should however never be applied via driver subsystem tree,
+     but always via platform SoC trees on dedicated branches (see also
+     Documentation/process/maintainer-soc.rst).
+
 III. Notes
 ==========