[POWERPC] Update interrupt info in booting-without-of.txt

Create a new section descrbing how interrupts are represented
in the device tree.  Added more detail.  Clarified some things.
Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

Documentation/powerpc/booting-without-of.txt

@@ -1108,42 +1108,7 @@ See appendix A for an example partial SOC node definition for the
 MPC8540.
 
 
-2) Specifying interrupt information for SOC devices
----------------------------------------------------
-
-Each device that is part of an SOC and which generates interrupts
-should have the following properties:
-
-	- interrupt-parent : contains the phandle of the interrupt
-          controller which handles interrupts for this device
-	- interrupts : a list of tuples representing the interrupt
-          number and the interrupt sense and level for each interrupt
-          for this device.
-
-This information is used by the kernel to build the interrupt table
-for the interrupt controllers in the system.
-
-Sense and level information should be encoded as follows:
-
-   Devices connected to openPIC-compatible controllers should encode
-   sense and polarity 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
-
-   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
-
-
-
-3) Representing devices without a current OF specification
+2) Representing devices without a current OF specification
 ----------------------------------------------------------
 
 Currently, there are many devices on SOCs that do not have a standard
@@ -1732,6 +1697,92 @@ platforms are moved over to use the flattened-device-tree model.
 
    More devices will be defined as this spec matures.
 
+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
+
 
 Appendix A - Sample SOC node for MPC8540
 ========================================