[U-Boot] Ease of porting Linux drivers/features to U-Boot?

Hi,

I'm still trying to figure out how to get support for my AR7-based board into U-Boot. There is support for the board in Linux, but some fundamental pieces are missing from U-Boot.

E.g. support for the VLYNQ bus that connects the network interface to the CPU, at the very least.

How difficult is it to port such things from Linux to U-Boot? Is it as simple as copying files from the Linux sources, and a little glue to enable linking them in (similar to how the UBIFS stuff has been introduced), or is it a lot more complex than that?

Thanks

Rogan