|  | PCI bus bridges have standardized Device Tree bindings: | 
|  |  | 
|  | PCI Bus Binding to: IEEE Std 1275-1994 | 
|  | http://www.openfirmware.org/ofwg/bindings/pci/pci2_1.pdf | 
|  |  | 
|  | And for the interrupt mapping part: | 
|  |  | 
|  | Open Firmware Recommended Practice: Interrupt Mapping | 
|  | http://www.openfirmware.org/1275/practice/imap/imap0_9d.pdf | 
|  |  | 
|  | Additionally to the properties specified in the above standards a host bridge | 
|  | driver implementation may support the following properties: | 
|  |  | 
|  | - linux,pci-domain: | 
|  | If present this property assigns a fixed PCI domain number to a host bridge, | 
|  | otherwise an unstable (across boots) unique number will be assigned. | 
|  | It is required to either not set this property at all or set it for all | 
|  | host bridges in the system, otherwise potentially conflicting domain numbers | 
|  | may be assigned to root buses behind different host bridges.  The domain | 
|  | number for each host bridge in the system must be unique. |