dt-bindings: Add rpm-smd documentation for holi

Add documentation for rpm-smd node.

Change-Id: Ic9cda94987c0d4849f462eae5ab3793411522ca6

bindings/arm/msm/rpm-smd.txt

@@ -0,0 +1,40 @@
+Resource Power Manager(RPM)
+
+RPM is a dedicated hardware engine for managing shared SoC resources,
+which includes buses, clocks, power rails, etc.  The goal of RPM is
+to achieve the maximum power savings while satisfying the SoC's
+operational and performance requirements.  RPM accepts resource
+requests from multiple RPM masters.  It arbitrates and aggregates
+the requests, and configures the shared resources. The RPM masters
+are the application processor, the modem processor, as well as hardware
+accelerators. The RPM driver communicates with the hardware engine using
+SMD.
+
+The devicetree representation of the RPM block should be:
+
+Required properties
+
+- compatible: "qcom,rpm-smd"
+- rpm-channel-name: The string corresponding to the channel name of the
+			peripheral subsystem. Required for both smd and
+			glink transports.
+- rpm-channel-type: The interal SMD edge for this subsystem found in
+			<soc/qcom/smd.h>
+- interrupts: The IRQ used by remote processor to inform APSS about
+				reception of response message packet.
+
+Optional properties
+- rpm-standalone: Allow RPM driver to run in standalone mode irrespective of RPM
+			channel presence.
+- reg: Contains the memory address at which rpm messaging format version is
+  stored. If this field is not present, the target only supports v0 format.
+
+Example:
+
+	qcom,rpm-smd {
+		compatible = "qcom,rpm-smd";
+		interrupts = <GIC_SPI 194 IRQ_TYPE_EDGE_RISING>;
+		qcom,rpm-channel-name = "rpm_requests";
+		qcom,rpm-channel-type = 15; /* APPS_RPM_SMD */
+	}
+}