dt/bindings: Add bindings for PIC32 interrupt controller

Document the devicetree bindings for the interrupt controller on
Microchip PIC32 class devices.

Signed-off-by: Cristian Birsan <cristian.birsan@microchip.com>
Signed-off-by: Joshua Henderson <joshua.henderson@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12093/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/Documentation/devicetree/bindings/interrupt-controller/microchip,pic32-evic.txt b/Documentation/devicetree/bindings/interrupt-controller/microchip,pic32-evic.txt
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+Microchip PIC32 Interrupt Controller
+====================================
+
+The Microchip PIC32 contains an Enhanced Vectored Interrupt Controller (EVIC).
+It handles all internal and external interrupts. This controller exists outside
+of the CPU and is the arbitrator of all interrupts (including interrupts from
+the CPU itself) before they are presented to the CPU.
+
+External interrupts have a software configurable edge polarity. Non external
+interrupts have a type and polarity that is determined by the source of the
+interrupt.
+
+Required properties
+-------------------
+
+- compatible: Should be "microchip,pic32mzda-evic"
+- reg: Specifies physical base address and size of register range.
+- interrupt-controller: Identifies the node as an interrupt controller.
+- #interrupt cells: Specifies the number of cells used to encode an interrupt
+  source connected to this controller. The value shall be 2 and interrupt
+  descriptor shall have the following format:
+
+       <hw_irq irq_type>
+
+  hw_irq - represents the hardware interrupt number as in the data sheet.
+  irq_type - is used to describe the type and polarity of an interrupt. For
+  internal interrupts use IRQ_TYPE_EDGE_RISING for non persistent interrupts and
+  IRQ_TYPE_LEVEL_HIGH for persistent interrupts. For external interrupts use
+  IRQ_TYPE_EDGE_RISING or IRQ_TYPE_EDGE_FALLING to select the desired polarity.
+
+Optional properties
+-------------------
+- microchip,external-irqs: u32 array of external interrupts with software
+  polarity configuration. This array corresponds to the bits in the INTCON
+  SFR.
+
+Example
+-------
+
+evic: interrupt-controller@1f810000 {
+       compatible = "microchip,pic32mzda-evic";
+       interrupt-controller;
+       #interrupt-cells = <2>;
+       reg = <0x1f810000 0x1000>;
+       microchip,external-irqs = <3 8 13 18 23>;
+};
+
+Each device/peripheral must request its interrupt line with the associated type
+and polarity.
+
+Internal interrupt DTS snippet
+------------------------------
+
+device@1f800000 {
+       ...
+       interrupts = <113 IRQ_TYPE_LEVEL_HIGH>;
+       ...
+};
+
+External interrupt DTS snippet
+------------------------------
+
+device@1f800000 {
+       ...
+       interrupts = <3 IRQ_TYPE_EDGE_RISING>;
+       ...
+};