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Documentation/devicetree/bindings/arm/spear/shirq.txt

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+* SPEAr Shared IRQ layer (shirq)
+
+SPEAr3xx architecture includes shared/multiplexed irqs for certain set
+of devices. The multiplexor provides a single interrupt to parent
+interrupt controller (VIC) on behalf of a group of devices.
+
+There can be multiple groups available on SPEAr3xx variants but not
+exceeding 4. The number of devices in a group can differ, further they
+may share same set of status/mask registers spanning across different
+bit masks. Also in some cases the group may not have enable or other
+registers. This makes software little complex.
+
+A single node in the device tree is used to describe the shared
+interrupt multiplexor (one node for all groups). A group in the
+interrupt controller shares config/control registers with other groups.
+For example, a 32-bit interrupt enable/disable config register can
+accommodate upto 4 interrupt groups.
+
+Required properties:
+  - compatible: should be, either of
+     - "st,spear300-shirq"
+     - "st,spear310-shirq"
+     - "st,spear320-shirq"
+  - interrupt-controller: Identifies the node as an interrupt controller.
+  - #interrupt-cells: should be <1> which basically contains the offset
+    (starting from 0) of interrupts for all the groups.
+  - reg: Base address and size of shirq registers.
+  - interrupts: The list of interrupts generated by the groups which are
+    then connected to a parent interrupt controller. Each group is
+    associated with one of the interrupts, hence number of interrupts (to
+    parent) is equal to number of groups. The format of the interrupt
+    specifier depends in the interrupt parent controller.
+
+  Optional properties:
+  - interrupt-parent: pHandle of the parent interrupt controller, if not
+    inherited from the parent node.
+
+Example:
+
+The following is an example from the SPEAr320 SoC dtsi file.
+
+shirq: interrupt-controller@0xb3000000 {
+	compatible = "st,spear320-shirq";
+	reg = <0xb3000000 0x1000>;
+	interrupts = <28 29 30 1>;
+	#interrupt-cells = <1>;
+	interrupt-controller;
+};