[U-Boot] sunxi: add custom board

[Giulio Benetti]

Hello Jagan and Maxime,

I've looked around a lot, but I can't find a way to use the board/sunxi:
http://git.denx.de/?p=u-boot.git;a=tree;f=board/sunxi;h=304ee6b4cc8e075759d3bd0beb250b56f6901702;hb=HEAD

to fit what we need.

We have 5 gpios that control the max current setting on current-driver 
for Backlight biasing shunt kathode resistor, and I don't know where to 
place the code to set those pins.

I would like to avoid to create another new board if possible, since 
board/sunxi has everything we need to make our board operative.
In general, is there some sort of __weak__ hooks to be used to extend an 
existing board?
Because I understand that probably you wouldn't add this code I'm 
talking about inside board/sunxi.

This request is done with idea to upstream patch for this board.

Can you help me?

Thanks in advance
Best regards
-- 
Giulio Benetti
CTO

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