There's plenty of hints that I haven't yet fleshed out and are hardcoded
in arswitch_8327.c. They're listed here (from OpenWRT) for completeness.
This is enough to get the thing up, running and pinging.
Note that the mdiobus for the on-switch switch changes - the AR8327
probes first, which exposes mdio1, and thus the arge1 mdiobus will probe
and attach as mdio2. That is what the AR9344 on-chip switch has to
attach to.
Tested:
* Qualcomm Atheros DB120
2e3fd37d45