Rbl ubl uboot

QUOTE:

1. RBL - Rom bootloader - embedded in the chip

2. UBL - User boot loader - NOT in the chip - RBL boots UBL (except for NOR and UART boot modes) which boots a secondary bootloader. There are size constraints on what RBL can boot and since most secondary bootloaders do not fit in the size UBL is required - provided by PSP

3. UBoot - secondary bootloader that PSP provides - typically used to boot linux kernel.