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+* Generic PCI host controller
+
+Firmware-initialised PCI host controllers and PCI emulations, such as the
+virtio-pci implementations found in kvmtool and other para-virtualised
+systems, do not require driver support for complexities such as regulator
+and clock management. In fact, the controller may not even require the
+configuration of a control interface by the operating system, instead
+presenting a set of fixed windows describing a subset of IO, Memory and
+Configuration Spaces.
+
+Such a controller can be described purely in terms of the standardized device
+tree bindings communicated in pci.txt:
+
+
+Properties of the host controller node:
+
+- compatible     : Must be "pci-host-cam-generic" or "pci-host-ecam-generic"
+                   depending on the layout of configuration space (CAM vs
+                   ECAM respectively).
+
+- device_type    : Must be "pci".
+
+- ranges         : As described in IEEE Std 1275-1994, but must provide
+                   at least a definition of non-prefetchable memory. One
+                   or both of prefetchable Memory and IO Space may also
+                   be provided.
+
+- bus-range      : Optional property (also described in IEEE Std 1275-1994)
+                   to indicate the range of bus numbers for this controller.
+                   If absent, defaults to <0 255> (i.e. all buses).
+
+- #address-cells : Must be 3.
+
+- #size-cells    : Must be 2.
+
+- reg            : The Configuration Space base address and size, as accessed
+                   from the parent bus.
+
+
+Properties of the /chosen node:
+
+- linux,pci-probe-only
+                 : Optional property which takes a single-cell argument.
+                   If '0', then Linux will assign devices in its usual manner,
+                   otherwise it will not try to assign devices and instead use
+                   them as they are configured already.
+
+Configuration Space is assumed to be memory-mapped (as opposed to being
+accessed via an ioport) and laid out with a direct correspondence to the
+geography of a PCI bus address by concatenating the various components to
+form an offset.
+
+For CAM, this 24-bit offset is:
+
+        cfg_offset(bus, device, function, register) =
+                   bus << 16 | device << 11 | function << 8 | register
+
+Whilst ECAM extends this by 4 bits to accomodate 4k of function space:
+
+        cfg_offset(bus, device, function, register) =
+                   bus << 20 | device << 15 | function << 12 | register
+
+Interrupt mapping is exactly as described in `Open Firmware Recommended
+Practice: Interrupt Mapping' and requires the following properties:
+
+- #interrupt-cells   : Must be 1
+
+- interrupt-map      : <see aforementioned specification>
+
+- interrupt-map-mask : <see aforementioned specification>
+
+
+Example:
+
+pci {
+    compatible = "pci-host-cam-generic"
+    device_type = "pci";
+    #address-cells = <3>;
+    #size-cells = <2>;
+    bus-range = <0x0 0x1>;
+
+    // CPU_PHYSICAL(2)  SIZE(2)
+    reg = <0x0 0x40000000  0x0 0x1000000>;
+
+    // BUS_ADDRESS(3)  CPU_PHYSICAL(2)  SIZE(2)
+    ranges = <0x01000000 0x0 0x01000000  0x0 0x01000000  0x0 0x00010000>,
+             <0x02000000 0x0 0x41000000  0x0 0x41000000  0x0 0x3f000000>;
+
+
+    #interrupt-cells = <0x1>;
+
+    // PCI_DEVICE(3)  INT#(1)  CONTROLLER(PHANDLE)  CONTROLLER_DATA(3)
+    interrupt-map = <  0x0 0x0 0x0  0x1  &gic  0x0 0x4 0x1
+                     0x800 0x0 0x0  0x1  &gic  0x0 0x5 0x1
+                    0x1000 0x0 0x0  0x1  &gic  0x0 0x6 0x1
+                    0x1800 0x0 0x0  0x1  &gic  0x0 0x7 0x1>;
+
+    // PCI_DEVICE(3)  INT#(1)
+    interrupt-map-mask = <0xf800 0x0 0x0  0x7>;
+}