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/siox/eckelmann,siox-gpio.txt

@@ -0,0 +1,19 @@
+Eckelmann SIOX GPIO bus
+
+Required properties:
+- compatible : "eckelmann,siox-gpio"
+- din-gpios, dout-gpios, dclk-gpios, dld-gpios: references gpios for the
+    corresponding bus signals.
+
+Examples:
+
+        siox {
+                compatible = "eckelmann,siox-gpio";
+                pinctrl-names = "default";
+                pinctrl-0 = <&pinctrl_siox>;
+
+                din-gpios = <&gpio6 11 0>;
+                dout-gpios = <&gpio6 8 0>;
+                dclk-gpios = <&gpio6 9 0>;
+                dld-gpios = <&gpio6 10 0>;
+        };