dt-bindings: soc: qcom: Add AOSS QMP binding

Add binding for the QMP based side-channel communication mechanism to
the AOSS, which is used to control resources not exposed through the
RPMh interface.
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Documentation/devicetree/bindings/soc/qcom/qcom,aoss-qmp.txt

+Qualcomm Always-On Subsystem side channel binding
+
+This binding describes the hardware component responsible for side channel
+requests to the always-on subsystem (AOSS), used for certain power management
+requests that is not handled by the standard RPMh interface. Each client in the
+SoC has it's own block of message RAM and IRQ for communication with the AOSS.
+The protocol used to communicate in the message RAM is known as Qualcomm
+Messaging Protocol (QMP)
+
+The AOSS side channel exposes control over a set of resources, used to control
+a set of debug related clocks and to affect the low power state of resources
+related to the secondary subsystems. These resources are exposed as a set of
+power-domains.
+
+- compatible:
+	Usage: required
+	Value type: <string>
+	Definition: must be "qcom,sdm845-aoss-qmp"
+
+- reg:
+	Usage: required
+	Value type: <prop-encoded-array>
+	Definition: the base address and size of the message RAM for this
+		    client's communication with the AOSS
+
+- interrupts:
+	Usage: required
+	Value type: <prop-encoded-array>
+	Definition: should specify the AOSS message IRQ for this client
+
+- mboxes:
+	Usage: required
+	Value type: <prop-encoded-array>
+	Definition: reference to the mailbox representing the outgoing doorbell
+		    in APCS for this client, as described in mailbox/mailbox.txt
+
+- #clock-cells:
+	Usage: optional
+	Value type: <u32>
+	Definition: must be 0
+		    The single clock represents the QDSS clock.
+
+- #power-domain-cells:
+	Usage: optional
+	Value type: <u32>
+	Definition: must be 1
+		    The provided power-domains are:
+		    CDSP state (0), LPASS state (1), modem state (2), SLPI
+		    state (3), SPSS state (4) and Venus state (5).
+
+= SUBNODES
+The AOSS side channel also provides the controls for three cooling devices,
+these are expressed as subnodes of the QMP node. The name of the node is used
+to identify the resource and must therefor be "cx", "mx" or "ebi".
+
+- #cooling-cells:
+	Usage: optional
+	Value type: <u32>
+	Definition: must be 2
+
+= EXAMPLE
+
+The following example represents the AOSS side-channel message RAM and the
+mechanism exposing the power-domains, as found in SDM845.
+
+  aoss_qmp: qmp@c300000 {
+	  compatible = "qcom,sdm845-aoss-qmp";
+	  reg = <0x0c300000 0x100000>;
+	  interrupts = <GIC_SPI 389 IRQ_TYPE_EDGE_RISING>;
+	  mboxes = <&apss_shared 0>;
+
+	  #power-domain-cells = <1>;
+
+	  cx_cdev: cx {
+		#cooling-cells = <2>;
+	  };
+
+	  mx_cdev: mx {
+		#cooling-cells = <2>;
+	  };
+  };

include/dt-bindings/power/qcom-aoss-qmp.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2018, Linaro Ltd. */
+
+#ifndef __DT_BINDINGS_POWER_QCOM_AOSS_QMP_H
+#define __DT_BINDINGS_POWER_QCOM_AOSS_QMP_H
+
+#define AOSS_QMP_LS_CDSP		0
+#define AOSS_QMP_LS_LPASS	1
+#define AOSS_QMP_LS_MODEM	2
+#define AOSS_QMP_LS_SLPI		3
+#define AOSS_QMP_LS_SPSS		4
+#define AOSS_QMP_LS_VENUS	5
+
+#endif