tests: drivers: pwm: loopback: add support for twr_ke18f board

Add support for testing the NXP Kinetis Pulse Width Timer (PWT) on the
NXP TWR-KE18F development board using PWM loopback.

Signed-off-by: Henrik Brix Andersen <[email protected]>

Author: henrikbrixandersen

tests/drivers/pwm/pwm_loopback/boards/twr_ke18f.overlay

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2020-2021 Vestas Wind Systems A/S
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <dt-bindings/pwm/pwm.h>
+
+/ {
+	pwm_loopback_0 {
+		compatible = "test,pwm_loopback";
+		pwms = <&ftm2 6 0 PWM_POLARITY_NORMAL>, /* PTE15, J20 pin 5 */
+		       <&pwt 1 0 PWM_POLARITY_NORMAL>;  /* PTE11, J20 pin 8 */
+	};
+};
+
+&pwt {
+	status = "okay";
+	prescaler = <32>;
+};
+
+&ftm2 {
+	status = "okay";
+	compatible = "nxp,kinetis-ftm-pwm";
+	prescaler = <128>;
+	#pwm-cells = <3>;
+};