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/cdns,xtensa-mx.txt

@@ -0,0 +1,18 @@
+* Xtensa Interrupt Distributor and Programmable Interrupt Controller (MX)
+
+Required properties:
+- compatible: Should be "cdns,xtensa-mx".
+
+Remaining properties have exact same meaning as in Xtensa PIC
+(see cdns,xtensa-pic.txt).
+
+Examples:
+	pic: pic {
+		compatible = "cdns,xtensa-mx";
+		/* one cell: internal irq number,
+		 * two cells: second cell == 0: internal irq number
+		 *            second cell == 1: external irq number
+		 */
+		#interrupt-cells = <2>;
+		interrupt-controller;
+	};