[U-Boot] Booting on RK3399

[Simon Glass]

Hi Kever,

I have a firefly-rk3399 and would like to boot it into U-Boot (as a start)
from an uSD card.

Are there instructions somewhere on how to do this? I gather that I need
OP-TEE but not how to build it or how to put the image together. I would
like to have instructions in README.rockchip if possible.

I'm planning to add U-Boot support for bob and maybe kevin (both
Chromebooks) but am not sure where to start. I thought the firefly might be
best since it is pretty common.

Thanks for any help you can provide.

Regards,
Simon