dt-bindings: Add devicetree bindings

Add snapshot of device tree bindings from keystone common kernel, branch
"android-mainline-keystone-qcom-release" at c4c12103f9c0 ("Snap for 9228065
from e32903b9a63bb558df8b803b076619c53c16baad to
android-mainline-keystone-qcom-release").

Change-Id: I7682079615cbd9f29340a5c1f2a1d84ec441a1f1
Signed-off-by: Melody Olvera <quic_molvera@quicinc.com>

bindings/interrupt-controller/al,alpine-msix.txt

@@ -0,0 +1,25 @@
+Alpine MSIX controller
+
+See arm,gic-v3.txt for SPI and MSI definitions.
+
+Required properties:
+
+- compatible: should be "al,alpine-msix"
+- reg: physical base address and size of the registers
+- interrupt-controller: identifies the node as an interrupt controller
+- msi-controller: identifies the node as an PCI Message Signaled Interrupt
+		  controller
+- al,msi-base-spi: SPI base of the MSI frame
+- al,msi-num-spis: number of SPIs assigned to the MSI frame, relative to SPI0
+
+Example:
+
+msix: msix {
+	compatible = "al,alpine-msix";
+	reg = <0x0 0xfbe00000 0x0 0x100000>;
+	interrupt-parent = <&gic>;
+	interrupt-controller;
+	msi-controller;
+	al,msi-base-spi = <160>;
+	al,msi-num-spis = <160>;
+};