dt-bindings: Introduce QCOM Sleep stats bindings

Add device binding documentation for Qualcomm Technologies, Inc. (QTI)
Sleep stats driver. The driver is used for displaying Sleep statistic maintained
by Always On Processor or Resource Power Manager.

Cc: devicetree@vger.kernel.org
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>
Signed-off-by: Lina Iyer <ilina@codeaurora.org>
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/1634107104-22197-2-git-send-email-mkshah@codeaurora.org

Documentation/devicetree/bindings/soc/qcom/qcom-stats.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/soc/qcom/qcom-stats.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Qualcomm Technologies, Inc. (QTI) Stats bindings
+
+maintainers:
+  - Maulik Shah <mkshah@codeaurora.org>
+
+description:
+  Always On Processor/Resource Power Manager maintains statistics of the SoC
+  sleep modes involving powering down of the rails and oscillator clock.
+
+  Statistics includes SoC sleep mode type, number of times low power mode were
+  entered, time of last entry, time of last exit and accumulated sleep duration.
+
+properties:
+  compatible:
+    enum:
+      - qcom,rpmh-stats
+      - qcom,rpm-stats
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  # Example of rpmh sleep stats
+  - |
+    sram@c3f0000 {
+      compatible = "qcom,rpmh-stats";
+      reg = <0x0c3f0000 0x400>;
+    };
+  # Example of rpm sleep stats
+  - |
+    sram@4690000 {
+      compatible = "qcom,rpm-stats";
+      reg = <0x04690000 0x10000>;
+    };
+...