docs: dt: submitting-patches: Avoid 'YAML' in the subject and add an example

Patches adding new device bindings should avoid 'YAML' keyword in the
subject, because all bindings are supposed to be in DT schema format,
which uses YAML.  The DT schema is welcomed only in case of patches
doing conversion.  Effectively people get confused that subject should
not contain anything else than device name after the prefix, so add two
recommended examples.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20250713-dt-bindings-docs-v2-1-672c898054ae@linaro.org


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>