dt-bindings: mmc: Document support for partition table in mmc-card

Document support for defining a partition table in the mmc-card node.

This is needed if the eMMC doesn't have a partition table written and
the bootloader of the device load data by using absolute offset of the
block device. This is common on embedded device that have eMMC installed
to save space and have non removable block devices.

If an OF partition table is detected, any partition table written in the
eMMC will be ignored and won't be parsed.

eMMC provide a generic disk for user data and if supported (JEDEC 4.4+)
also provide two additional disk ("boot1" and "boot2") for special usage
of boot operation where normally is stored the bootloader or boot info.
New JEDEC version also supports up to 4 GP partition for other usage
called "gp1", "gp2", "gp3", "gp4".

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20241002221306.4403-7-ansuelsmth@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>