Pre-built U-Boot binaries in this directory are:

  u-boot-tpl.bin - U-Boot TPL or Rockchip ddrbin. First stage of the bootloader
                   that initializes DRAM.
  
  u-boot-spl.bin - U-Boot SPL. Second stage bootloader that is loaded to DRAM
                   and is expected to load main U-Boot binary (u-boot.itb)
                   from somewhere.

  u-boot.itb - main U-Boot binary image that is intended to be loaded
               and executed by U-Boot SPL. It needs to be flashed to a
               location where SPL can find it. Usually sector 16384 on
               SD or eMMC or to an offset in SPI NOR flash that's configured
               in SPL's embedded DTB in /config/u-boot,spl-payload-offset
               proprety. Use rk2aw-spi-flasher to flash this to SPI NOR flash
               unless you know absolutely exactly what you're doing.

  idbloader.img - boot block image containing U-Boot TPL + SPL or Rockchip
                  ddrbin + U-Boot SPL. You can flash this to one of the
                  Rockchip boot blocks. This is basically a combination
                  of u-boot-tpl.bin + u-boot-spl.bin + a BROM boot image
                  header.

  u-boot-rockchip.bin - combined idbloader.img + u-boot.itb for flashing
                  to boot block 64 on SD or eMMC (this is just a
                  convenience image)

  .config - Full U-Boot config file used to build the above binaries.
            You can use it to reproduce the build and/or check what
            features are enabled in this particular build.