1PCI bus bridges have standardized Device Tree bindings:
2
3PCI Bus Binding to: IEEE Std 1275-1994
4http://www.firmware.org/1275/bindings/pci/pci2_1.pdf
5
6And for the interrupt mapping part:
7
8Open Firmware Recommended Practice: Interrupt Mapping
9http://www.firmware.org/1275/practice/imap/imap0_9d.pdf
10
11Additionally to the properties specified in the above standards a host bridge
12driver implementation may support the following properties:
13
14- linux,pci-domain:
15   If present this property assigns a fixed PCI domain number to a host bridge,
16   otherwise an unstable (across boots) unique number will be assigned.
17   It is required to either not set this property at all or set it for all
18   host bridges in the system, otherwise potentially conflicting domain numbers
19   may be assigned to root buses behind different host bridges.  The domain
20   number for each host bridge in the system must be unique.
21