gpu: ipu-v3: add DT binding for the Prefetch Resolve Engine

The Prefetch Resolve Engine is a prefetch and tile resolve engine
which prefetches display data from DRAM to an internal SRAM region.
It has a single clock for configuration register access and the
functional units. A single shared interrupt is used for status and
error signaling.

The only external dependency is the SRAM region to use for the
prefetch double buffer.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

Documentation/devicetree/bindings/display/imx/fsl-imx-drm.txt

@@ -53,6 +53,32 @@ ipu: ipu@18000000 {
 	};
 };
 
+Freescale i.MX PRE (Prefetch Resolve Engine)
+============================================
+
+Required properties:
+- compatible: should be "fsl,imx6qp-pre"
+- reg: should be register base and length as documented in the
+  datasheet
+- clocks : phandle to the PRE axi clock input, as described
+  in Documentation/devicetree/bindings/clock/clock-bindings.txt and
+  Documentation/devicetree/bindings/clock/imx6q-clock.txt.
+- clock-names: should be "axi"
+- interrupts: should contain the PRE interrupt
+- fsl,iram: phandle pointing to the mmio-sram device node, that should be
+  used for the PRE SRAM double buffer.
+
+example:
+
+pre@21c8000 {
+	compatible = "fsl,imx6qp-pre";
+	reg = <0x021c8000 0x1000>;
+	interrupts = <GIC_SPI 90 IRQ_TYPE_EDGE_RISING>;
+	clocks = <&clks IMX6QDL_CLK_PRE0>;
+	clock-names = "axi";
+	fsl,iram = <&ocram2>;
+};
+
 Parallel display support
 ========================