Using phorn's switch-ip175c.c I was able to add support for the IP175C of the RB433 to kmod-switch. I figured out the port numbers of the three ethernet jacks (looking onto the front):
[port4] (serial) [port1] [port2]
where eth0 seems to be connected to port4 and eth1 to port1.
Remaining problem is that port2 is kind of unconnected to any netdevice and also a
doesn't show any information (neither "down" or "up"). I guess that's due to the fact that port2 is the _second_ PHY on MII0 and not properly enumerated on this mdio bus.