This new defconfig is introduced to support SPL boot from QSPI NOR flash. This is to support falcon mode for faster booting into Linux.
To use falcon mode with QSPI boot, SPL needs to be enabled. Similar to SD or NAND boot, a RAM version full feature U-Boot is needed. Unlike SD or NAND boot, SPL with QSPI doesn't need to combine SPL image with RAM version image. Two separated images are used, u-boot-spl.pbl and u-boot.img. The former is SPL image with RCW and PBI commands to load the SPL payload into On-Chip RAM. The latter is RAM version U-Boot in FIT format (or legacy format if FIT is not used).
Please program u-boot-spl.pbl at offset 0x0 and u-boot.img at offset 0x00100000 on QSPI flash.