Documentation/process: maintainer-soc: Document purpose of defconfigs

Documentation/process: maintainer-soc: Document purpose of defconfigs

Common mistake in commit messages of patches on mailing list adding
CONFIG options to arm/multi_v7 or arm64/defconfig is saying what that
patch is doing, e.g. "Enable driver foo".  That is obvious from the diff
part, thus explaining it does not bring any value.  What brings value is
to understand why "driver foo" should be in a shared, upstream
defconfig, especially considering that distros have their own defconfigs
and we do not care about non-upstream trees.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260413074401.27282-4-krzysztof.kozlowski@oss.qualcomm.com
Signed-off-by: Arnd Bergmann <arnd@arndb.de>