+VII - Specifying interrupt information for devices
+===================================================
+
+The device tree represents the busses and devices of a hardware
+system in a form similar to the physical bus topology of the
+hardware.
+
+In addition, a logical 'interrupt tree' exists which represents the
+hierarchy and routing of interrupts in the hardware.
+
+The interrupt tree model is fully described in the
+document "Open Firmware Recommended Practice: Interrupt
+Mapping Version 0.9". The document is available at:
+<http://playground.sun.com/1275/practice>.
+
+1) interrupts property
+----------------------
+
+Devices that generate interrupts to a single interrupt controller
+should use the conventional OF representation described in the
+OF interrupt mapping documentation.
+
+Each device which generates interrupts must have an 'interrupt'
+property. The interrupt property value is an arbitrary number of
+of 'interrupt specifier' values which describe the interrupt or
+interrupts for the device.
+
+The encoding of an interrupt specifier is determined by the
+interrupt domain in which the device is located in the
+interrupt tree. The root of an interrupt domain specifies in
+its #interrupt-cells property the number of 32-bit cells
+required to encode an interrupt specifier. See the OF interrupt
+mapping documentation for a detailed description of domains.
+
+For example, the binding for the OpenPIC interrupt controller
+specifies an #interrupt-cells value of 2 to encode the interrupt
+number and level/sense information. All interrupt children in an
+OpenPIC interrupt domain use 2 cells per interrupt in their interrupts
+property.
+
+The PCI bus binding specifies a #interrupt-cell value of 1 to encode
+which interrupt pin (INTA,INTB,INTC,INTD) is used.
+
+2) interrupt-parent property
+----------------------------
+
+The interrupt-parent property is specified to define an explicit
+link between a device node and its interrupt parent in
+the interrupt tree. The value of interrupt-parent is the
+phandle of the parent node.
+
+If the interrupt-parent property is not defined for a node, it's
+interrupt parent is assumed to be an ancestor in the node's
+_device tree_ hierarchy.
+
+3) OpenPIC Interrupt Controllers
+--------------------------------
+
+OpenPIC interrupt controllers require 2 cells to encode
+interrupt information. The first cell defines the interrupt
+number. The second cell defines the sense and level
+information.
+
+Sense and level information should be encoded as follows:
+
+ 0 = low to high edge sensitive type enabled
+ 1 = active low level sensitive type enabled
+ 2 = active high level sensitive type enabled
+ 3 = high to low edge sensitive type enabled
+
+4) ISA Interrupt Controllers
+----------------------------
+
+ISA PIC interrupt controllers require 2 cells to encode
+interrupt information. The first cell defines the interrupt
+number. The second cell defines the sense and level
+information.
+
+ISA PIC interrupt controllers should adhere to the ISA PIC
+encodings listed below:
+
+ 0 = active low level sensitive type enabled
+ 1 = active high level sensitive type enabled
+ 2 = high to low edge sensitive type enabled
+ 3 = low to high edge sensitive type enabled
+