dt-bindings: input: document Qualcomm PMI8998 haptics driver

Add bindings for qcom PMIC PMI8998 haptics driver.

Signed-off-by: Caleb Connolly <caleb@connolly.tech>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Documentation/devicetree/bindings/input/qcom,pmi8998-haptics.yaml

@@ -0,0 +1,73 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright 2020 Unisoc Inc.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/qcom,pmi8998-haptics.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Qualcomm PMI8998/PM660 Haptics
+
+maintainers:
+  - Caleb Connolly <caleb@connolly.tech>
+
+description: |
+  Qualcomm SPMI haptics is a peripheral on some QTI PMICs. It supports linear resonant
+  actuators and eccentric rotating mass type haptics commonly found in mobile devices.
+  It supports multiple sources of wave data such as an internal buffer, direct play
+  (from kernel or userspace) as well as an audio output mode.
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - qcom,pmi8998-haptics
+          - qcom,pm660-charger
+          - qcom,pmi8996-haptics
+          - qcom,pmi8941-haptics
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 2
+
+  interrupt-names:
+    items:
+      - const: short
+      - const: play
+
+  qcom,wave-play-duration-us:
+    description: |
+      Wave sample duration in microseconds, 1/f where f
+      is the resonant frequency of the actuator.
+      This property is named qcom,wave-play-rate-us in
+      downstream kernels.
+    minimum: 0
+    maximum: 20475
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - qcom,wave-play-rate-us
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    spmi {
+      #address-cells = <1>;
+      #size-cells = <0>;
+      pmi8998_haptics: haptics@c000 {
+        compatible = "qcom,pmi8998-haptics";
+        reg = <0xc000>;
+
+        interrupts = <0x3 0xc0 0x0 IRQ_TYPE_EDGE_BOTH>,
+                     <0x3 0xc0 0x1 IRQ_TYPE_EDGE_BOTH>;
+        interrupt-names = "short", "play";
+
+        qcom,wave-play-rate-us = <4255>;
+      };
+    };