Unfortunately, this isn't an acceptable change to the Rock64 dts file.
Yes, there's the second built-in Ethernet interface in the RK3328 SoC,
but the Rock64 layout doesn't expose it as a separate physical network
interface, i.e. it isn't available as a port.
I was wondering if the Rock64 lacks a port.
According to this link: https://pine64.org/devices/rock64/,
it seems that there is a physical network interface available on the sbc.
Such a change would be fine to be applied to the dts by hand, by someone
who actually adds a second physical network port to their Rock64.