Load GUIXSD with customized u-boot

[Farshid Karimi]

Hello

I want to load guixsd on an arm-based board "rock pi4".
from like this site (https://github.com/radxa/rockchip-bsp) i can generate
custom u-boot and kernel for this board.
If i have a generated u-boot.img how can i run guixsd as kernel.(like this
tutorial: https://guix.gnu.org/blog/2017/porting-guixsd-to-armv7/)
how i can customize u-boot and then use it beside an guixsd?

Regards.