Documentation/process: maintainer-soc: clarify submitting patches

Patches for SoCs are expected to be picked up by SoC submaintainers.
The main SoC maintainers should be addressed only in few cases.

Rewrite the section about maintainer handling to document above
expectation.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Will Deacon <will@kernel.org>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Conor Dooley <conor@kernel.org>
Cc: Heiko Stübner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20240925095635.30452-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Arnd Bergmann <arnd@arndb.de>