option: Allow mainboards to implement the API

Some mainboards need a mainboard-specific mechanism to access option
values. Allow mainboards to implement the option API. Also, add some
documentation about the current option API, and describe when should
one reimplement the option API in mainboard code: only when the code
is mainboard-specific to comply with externally-imposed constraints.

Change-Id: Idccdb9a008b1ebb89821961659f27b1c0b17d29c
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54729
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

0 files changed, 0 insertions, 0 deletions