Full "disable" DHCP on some interface(s)

Hi!

I’ve searched and read this forum and the wiki, but I haven’t found yet…
How can I disable complete DHCP ports on some interface?

Example: ether5 don’t receive & send DHCP packets. The router’s DHCP server doesn’t respond too!
So, I want “filter” external and internal DHCP packets on selected interface(s).

Thanks!