Question about porting OpenWrt on switch chip

hi, ALL:

I have a question about ethernet connection between CPU's eth0 and switch chip port. The switch chip has 8 ordinary port and a CPU port. The CPU port will add 16 bytes private header on the head of each ethernet frame. Then the CPU's eth0 should connect with switch chip's ordinary port or CPU port? If connect to CPU port, the eth0's driver should recognize the 16 bytes private header, I think it is impossible for the driver is on linux kernel. I think the eth0 should connect to switch chip's ordinary port, and I want to know other vendor OpenWRT board is also connect to switch chip‘s ordinary port?

Thanks!
Kun

That's basically DSA