docs: process: maintainer-soc-clean-dts: linux-next is decisive

Devicetree bindings patches go usually via driver subsystem tree, so
obviously testing only SoC branches would result in new dtbs_check
warnings.  Mention that linux-next branch is decisice for zero-warnings
rule.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250225184822.213296-2-krzysztof.kozlowski@linaro.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

Author: krzk

Documentation/process/maintainer-soc-clean-dts.rst

@@ -17,8 +17,9 @@ Strict DTS DT Schema and dtc Compliance
 No changes to the SoC platform Devicetree sources (DTS files) should introduce
 new ``make dtbs_check W=1`` warnings.  Warnings in a new board DTS, which are
 results of issues in an included DTSI file, are considered existing, not new
-warnings.  The platform maintainers have automation in place which should point
-out any new warnings.
+warnings.  For series split between different trees (DT bindings go via driver
+subsystem tree), warnings on linux-next are decisive.  The platform maintainers
+have automation in place which should point out any new warnings.
 
 If a commit introducing new warnings gets accepted somehow, the resulting
 issues shall be fixed in reasonable time (e.g. within one release) or the