dt-bindings: renesas: Document preferred compatible naming

dt-bindings: renesas: Document preferred compatible naming

Compatibles can come in two formats. Either "vendor,ip-soc" or
"vendor,soc-ip". Add a DT schema file documenting Renesas preferred
policy and enforcing it for all new compatibles, except few existing
patterns.

Suggested-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20240213224259.2967533-1-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>