[coreboot] Documentation for using util/vgabios with coreboot?

If one doesn't have/want to use a commercial VGA BIOS with coreboot ...

... how does one use util/vgabios with coreboot and integrated video?

Since the video signal is being generated by the chipset, it seems
that coreboot must do some video related chipset initialization
prior to running testbios (util/vgabios).

I assume this has been done on a few boards using coreboot v2.
Is there any documentation describing what needs to be done?
Can anyone describe the status of util/vgabios?

Thanks,

Ken Fuchs