gpio: imx-rpmsg: add rpmsg virtual gpio driver

Add rpmsg virtual gpio driver support.
i.MX7ULP GPIO PTA and PTB resource are managed by M4 core, setup one
simple protocol with M4 core based on RPMSG virtual IO to let A core
access such GPIOs that is what the driver do.

Signed-off-by: Fugang Duan <fugang.duan@nxp.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/gpio/gpio-imx-rpmsg.txt b/Documentation/devicetree/bindings/gpio/gpio-imx-rpmsg.txt
new file mode 100644
index 000000000000..49c7d321e2bf
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-imx-rpmsg.txt
@@ -0,0 +1,38 @@
+Device-Tree bindings for drivers/gpio/gpio-imx-rpmsg.c gpio driver over
+rpmsg. On i.mx7ULP PTA PTB are connected on M4 side, so rpmsg gpio driver
+needed to get/set gpio status from M4 side by rpmsg.
+
+Required properties:
+- compatible : Should be "fsl,imx-rpmsg-gpio".
+- port_idx : Specify the GPIO PORT index, PTA:0, PTB:1.
+- gpio-controller : Mark the device node as a gpio controller.
+- #gpio-cells : Should be two. The first cell is the pin number and
+  the second cell is used to specify the gpio polarity:
+      0 = active high
+      1 = active low
+
+Note: Each GPIO port should have an alias correctly numbered in "aliases"
+node.
+
+Examples:
+
+aliases {
+	gpio4 = &rpmsg_gpio0;
+	gpio5 = &rpmsg_gpio1;
+};
+
+rpmsg_gpio0: rpmsg-gpio0 {
+	compatible = "fsl,imx-rpmsg-gpio";
+	port_idx = <0>;
+	gpio-controller;
+	#gpio-cells = <2>;
+	status = "okay";
+};
+
+rpmsg_gpio1: rpmsg-gpio1 {
+	compatible = "fsl,imx-rpmsg-gpio";
+	port_idx = <1>;
+	gpio-controller;
+	#gpio-cells = <2>;
+	status = "okay";
+};