[PATCH] PCI: clean up pci documentation to be more specific

   See Documentation/IO-mapping.txt for how to access device memory.

   You still need to call request_region() for I/O regions and

request_mem_region() for memory regions to make sure nobody else is using the

same device.

   The device driver needs to call pci_request_region() to make sure

no other device is already using the same resource. The driver is expected

to determine MMIO and IO Port resource availability _before_ calling

pci_enable_device().  Conversely, drivers should call pci_release_region()

_after_ calling pci_disable_device(). The idea is to prevent two devices

colliding on the same address range.

Generic flavors of pci_request_region() are request_mem_region()

(for MMIO ranges) and request_region() (for IO Port ranges).

Use these for address resources that are not described by "normal" PCI

interfaces (e.g. BAR).

   All interrupt handlers should be registered with SA_SHIRQ and use the devid

to map IRQs to devices (remember that all PCI interrupts are shared).