Rock PI S dtb issue

#1

When I test the board.I confuse the question
CPU model RK3308BS
system rockpi-s-ubuntu-focal-server-arm64-20220308-0852-gpt.img.xz
root@rockpis:/home/drv# cat /boot/uEnv.txt

verbosity=7
fdtfile=rockchip/rk3308-rock-pi-s.dtb
console=ttyS0,1500000n8
overlays=rk3308-uart0 rk3308-uart1 rk3308-uart2 **rk3308-uart3**
rootuuid=2a975457-7408-4fda-bd37-22b8d2df5b6f
initrdsize=0x5c9a03
kernelversion=4.4.143-65-rockchip-g58431d38f8f3
initrdimg=initrd.img-4.4.143-65-rockchip-g58431d38f8f3
kernelimg=vmlinuz-4.4.143-65-rockchip-g58431d38f8f3

When I reboot ,the uart3 works

BUT when I test on my another board
CPU MODEL rk3308B
I can’t use UART3 .it seems rk3308-uart3 don’t support on old board

#2