bootdir= /boot
bootfile=zImage
fdtfile=am335x-boneblack.dtb
loadfdt=fatload mmc 0:1 ${fdtaddr} ${fdtfile}
loaduimage=fatload mmc 0:1 ${loadaddr} ${bootfile}
mmcroot=/dev/mmcblk0p2 
uenvcmd=mmc rescan; run loaduimage; run loadfdt; run fdtboot
fdtboot=run mmc_args; bootz ${loadaddr} - ${fdtaddr}
mmc_args=setenv bootargs console=${console} ${optargs} root=${mmcroot} rootfstype=${mmcrootfstype}