Back to your case. Board is cheap which is not all the time case for any
xilinx board but you have only uart, sd and partially described ethernet
which doesn't work without PL. Is it worth to have this described?
I got your point. But it is at least a jump start for the users if that
board boots out of the box. And yes, its unfortunate, that ethernet
just works if the PL is configured. This is already done by the
bootloader, because there I do have the same problem.
Zynq/ZynqMP boards can use U-Boot SPL. "Advantage" of this solution
especially for Zynq is that in u-boot there is open a way for adding
ps7_init file which is determined by device tree name.
I think it would make sense to add these DTs and also ps7_init to U-Boot
project and wire it up with zynq_virt platform and then you can boot
Linux with using U-Boot's DT pointed by $fdtcontroladdr.
Then you will get support from scratch to be able to boot.