dts: bindings: add binding for NXP Kinetis LPTMR

Add device tree binding for the NXP Kinetis Low Power Timer (LPTMR)
module. This module can either act as a 16 bit counter or a 16 bit
pulse counter.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>

dts/bindings/rtc/nxp,kinetis-lptmr.yaml

@@ -0,0 +1,33 @@
+# Copyright (c) 2020 Vestas Wind Systems A/S
+# SPDX-License-Identifier: Apache-2.0
+
+description: Kinetis LPTMR
+
+compatible: "nxp,kinetis-lptmr"
+
+include: rtc.yaml
+
+properties:
+    reg:
+      required: true
+
+    clock-frequency:
+      required: true
+
+    prescaler:
+      required: true
+
+    clk-source:
+      type: int
+      required: true
+      description: Prescaler clock source (0 to 3)
+
+    input-pin:
+      type: int
+      required: false
+      description: Pulse counter input pin (0 to 3).
+
+    active-low:
+      type: boolean
+      required: false
+      description: Pulse counter input pin is active-low