The document "PCI Bus Binding to: IEEE Std 1275-1994 Standard for Boot
(Initialization Configuration) Firmware" describes how the PCI topology
can be described in the DT, in order to augment the PCI devices with
additional information via DT properties.

This patch links OF nodes to the corresponding PCI devices if they
exist, allowing PCI device drivers to query DT information like any
platform device.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>