- Look for a hardwired interrupt in the routing table for this
bus/device/pin (we already did this).
- Look for another device with the same link byte which has a hardwired
interrupt.
- Look for a PCI device matching an entry with the same link byte
which has already been assigned an interrupt, and use that.
- Look for a routable interrupt listed in the "PCI only" interrupts
field and use that.
- Pick the first interrupt that's marked as routable and use that.