1. setenv ethaddr 42 6A C3 80 24 65
  2. setenv console tty0
  3. setenv stdout serial,vga
  4. setenv stderr serial,vga
  6. setenv scriptaddr 0x00500000
  7. setenv kernel_addr_r 0x02080000
  8. setenv fdt_addr_r 0x01f00000
  10. part uuid ${devtype} ${devnum}:${bootpart} uuid
  11. setenv bootargs earlyprintk debug=on loglevel=1 net.ifnames=0 console=ttyS2,1500000n8 console=tty0 root=PARTUUID=${uuid} rw rootfstype=ext4 fsck.repair=yes rootwait
  13. if load ${devtype} ${devnum}:${bootpart} ${kernel_addr_r} vmlinuz; then
  14. if load ${devtype} ${devnum}:2 ${fdt_addr_r} usr/lib/linux-image-5.5.0/rockchip/rk3399-rock-pi-4.dtb; then
  15. fdt addr ${fdt_addr_r}
  16. fdt resize
  17. #fdt set /ethernet@ff540000 local-mac-address "[${ethaddr}]"
  18. booti ${kernel_addr_r} - ${fdt_addr_r};
  19. fi;
  20. fi

I am loading dtb from rootfs 'usr/lib/linux-image-5.5.0/rockchip/rk3399-rock-pi-4.dtb'

Thats why I fixed :

load ${devtype} ${devnum}:2 <-----