I've been working on standardizing the u-boot builds in Debian, and one platform I've been working on moving over to config_distro_defaults is the BeagleBone Black...
In doing so, it took some moderate modification of config_distro_defaults to allow changing some hard-coded values, and implementing support for importing uEnv.txt files, and supporting alternate boot partitions.
I've worked on trying to keep the default behavior for the BeagleBone Black and other platforms that use am335x_evm.h relatively unchanged, though I don't really have the other platforms to test.
Haven't yet figured out u-boot's patch submission guidelines, and while I tried to maintain the existing coding style, checkpatch.pl produces quite a few errors on the patchset. If someone would be willing to help me get the patchset into shape for proper submission, that would be great.
For the moment, the patches are available here:
http://cascadia.debian.net/~vagrant/bootcmd-am335x/
Thanks!
live well, vagrant