Add devicetree binding for SPI devices.

Signed-off-by: Andrew Duggan <redacted>
---
 .../devicetree/bindings/input/rmi4/rmi_spi.txt     | 57 ++++++++++++++++++++++
 drivers/input/rmi4/rmi_spi.c                       | 44 ++++++++++++++++-
 2 files changed, 100 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/input/rmi4/rmi_spi.txt

diff --git a/Documentation/devicetree/bindings/input/rmi4/rmi_spi.txt b/Documentation/devicetree/bindings/input/rmi4/rmi_spi.txt
new file mode 100644
index 0000000..f20366b6
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/rmi4/rmi_spi.txt

@@ -0,0 +1,57 @@
+Synaptics RMI4 SPI Device Binding
+
+The Synaptics RMI4 core is able to support RMI4 devices using differnet
+transports and differnet functions. This file describes the device tree
+bindings for devices using the SPI tranport driver. Complete documentation
+for other transports and functions cen be found ini
+Documentation/devicetree/bindings/input/rmi4.
+
+Required Properties:
+- compatible: syna,rmi-spi
+- reg: Chip select address for the device
+- #address-cells: Set to 1 to indicate that the function child nodes
+		    consist of only on uint32 value.
+- #size-cells: Set to 0 to indicate that the function child nodes do not
+		have a size property.
+
+Optional Properties:
+- interrupts: interrupt which the rmi device is connected to.
+- interrupt-parent: The interrupt controller.
+See Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
+
+- syna,spi-read-delay: millisecond delay between read byte transfers.
+- syna,spi-write-delay: millisecond delay between write byte transfers.