Add initial support for NanoPi M4B, a minor revision of
the original NanoPi M4.

Commit details of rk3399-nanopi-m4b.dts sync from Linux 5.12-rc4:
"arm64: dts: rockchip: Add NanoPi M4B board"
(sha1: c7b03115003f7f337ab165542cee37148cf30a8a)

Signed-off-by: Alexandre Vicenzi <alexandre.vicenzi@suse.com>
Reviewed-by: Kever Yang <kever.yang@rock-cihps.com>

This would be useful and recommended boot flow for new boards
which has doesn't have the DDR support yet in mainline.

Sometimes it is very useful for debugging mainline DDR support.

Documen it for px30 boot flow.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang<kever.yang@rock-chips.com>

Document SPI flash program steps for rockchip platforms.

Suggested-by: Hugh Cole-Baker <sigmaris@gmail.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

This commit add the default configuration file and relevant description
for rock-pi-e board

Signed-off-by: Banglang Huang <banglang.huang@foxmail.com>

Update the list of supported boards with the information available
on doc/README.rockchip.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

As an additional step to move documentation to doc/boards/rockchip
improve format of the supported board list to make it more readable.
Additionally, add the configuration files used to build them based on
doc/README.rockchip.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

Document eMMC partition creation and program steps for
rockchip platforms.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

Rockchip has documentation file, doc/README.rockchip but
which is not so readable to add or understand the existing
contents. Even the format that support is legacy readme
in U-Boot.

Add rockchip specific documentation file using new rst
format, which describes the information about Rockchip
supported boards and it's usage steps.

Added minimal information about rk3288, rk3328, rk3368
and rk3399 boards and usage. This would indeed updated
further based on the requirements and updates.

Cc: Kever Yang <kever.yang@rock-chips.com>
Cc: Matwey V. Kornilov <matwey.kornilov@gmail.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>