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@68150 {
		compatible = "qcom,rpm-smd";
		reg = <0x68150 0x3200>;
		interrupts = <GIC_SPI 168 IRQ_TYPE_EDGE_RISING>;
		qcom,rpm-channel-name = "rpm_requests";
		qcom,rpm-channel-type = 15; /* SMD_APPS_RPM */
	}
}