dt-bindings: pinctrl: Add binding for ZynqMP pinctrl driver

Adding documentation and dt-bindings file which contains MIO pin
configuration defines for Xilinx ZynqMP pinctrl driver.
Signed-off-by: Sai Krishna Potthuri <lakshmi.sai.krishna.potthuri@xilinx.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1618485193-5403-3-git-send-email-lakshmi.sai.krishna.potthuri@xilinx.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

include/dt-bindings/pinctrl/pinctrl-zynqmp.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * MIO pin configuration defines for Xilinx ZynqMP
+ *
+ * Copyright (C) 2020 Xilinx, Inc.
+ */
+
+#ifndef _DT_BINDINGS_PINCTRL_ZYNQMP_H
+#define _DT_BINDINGS_PINCTRL_ZYNQMP_H
+
+/* Bit value for different voltage levels */
+#define IO_STANDARD_LVCMOS33	0
+#define IO_STANDARD_LVCMOS18	1
+
+/* Bit values for Slew Rates */
+#define SLEW_RATE_FAST		0
+#define SLEW_RATE_SLOW		1
+
+#endif /* _DT_BINDINGS_PINCTRL_ZYNQMP_H */