[PATCH 1/2] Doc: DT: Add binding document for GPIO exporter

[Martin Fuzzey <mfuzzey@xxxxxxxxxxx>]

Signed-off-by: Martin Fuzzey <mfuzzey@xxxxxxxxxxx>
---
 .../devicetree/bindings/gpio/gpio-exporter.txt     |   40 ++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-exporter.txt

diff --git a/Documentation/devicetree/bindings/gpio/gpio-exporter.txt b/Documentation/devicetree/bindings/gpio/gpio-exporter.txt
new file mode 100644
index 0000000..58fc2a9
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-exporter.txt
@@ -0,0 +1,40 @@
+Bindings to export some GPIOs to userspace.
+
+This is useful when some signals are made externally available by a piece
+of hardware (eg terminal blocks to connect sensors, actuators) but no
+special purpose kernel driver exists.
+
+Use of this binding allows userspace to have a stable name and input
+/ output mode across hardware and software versions.
+
+Required properties:
+- compatible: "linux,gpio-exporter"
+
+
+Each GPIO to be exported is represented as a child node with:
+
+Required child properties:
+- gpios : Reference to the GPIO to export (standard gpio binding)
+
+Optional child properties:
+- output : if present GPIO is output, otherwise input
+- initial-state : Initial state (0=low, 1=high) for output
+- allow-direction-change : Present if GPIO direction may be modified
+
+The name of the child node is that exposed to userspace.
+
+Example:
+	gpio_exporter:gpio-exporter {
+		compatible = "linux,gpio-exporter";
+
+		terminalblock_1_out1 {
+			gpios = <&gpio2 12 0>;
+			output;
+			initial-state = <0>;
+		};
+
+		terminalblock_1_in1 {
+			gpios = <&gpio2 15 0>;
+		};
+
+	};

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