Hey all,
I've been thinking about one of the problems we need to solve over in TI AM335x land and that is given that we support a number of different boards with a single binary (and we have an i2c eeprom that tells us what board and revision we are on), the user needs to be able to easily determine what board we are on so they know what dtb file to load so they can boot. To this end I've added CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG to the README which says when set we have board_name and board_rev set at run-time. Then for am335x[1] set that and CONFIG_BOARD_LATE_INIT which will set the variables and add a command, findfdt to compare and set fdtfile correctly. Further distro-specific logic can then augment this to figure out what filesystem / partition to read from.
[1]: Yes, this will need re-working after merging Peter K's patches to allow for non-TI boards.