Describe a cyclonei-ps-spi devicetree entry, required features

Signed-off-by: Joshua Clayton <stillcompil...@gmail.com>
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 .../bindings/fpga/cyclone-ps-spi-fpga-mgr.txt      | 23 ++++++++++++++++++++++
 1 file changed, 23 insertions(+)
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Documentation/devicetree/bindings/fpga/cyclone-ps-spi-fpga-mgr.txt

diff --git a/Documentation/devicetree/bindings/fpga/cyclone-ps-spi-fpga-mgr.txt 
b/Documentation/devicetree/bindings/fpga/cyclone-ps-spi-fpga-mgr.txt
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index 0000000..c942281
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+Altera Cyclone Passive Serial SPI FPGA Manager
+
+Altera Cyclone FPGAs support a method of loading the bitstream over what is
+referred to as "passive serial".
+The passive serial link is not technically spi, and might require extra
+circuits in order to play nicely with other spi slaves on the same bus.
+
+See https://www.altera.com/literature/hb/cyc/cyc_c51013.pdf
+
+Required properties:
+- compatible  : should contain "altr,cyclone-ps-spi-fpga-mgr"
+- reg         : spi slave id of the fpga
+- config-gpio : config pin (referred to as nCONFIG in the cyclone manual)
+- status-gpio : status pin (referred to as nSTATUS in the cyclone manual)
+
+Example:
+       fpga_spi: evi-fpga-spi@0 {
+               compatible = "altr,cyclone-ps-spi-fpga-mgr";
+               spi-max-frequency = <20000000>;
+               reg = <0>;
+               config-gpio = <&gpio4 9 GPIO_ACTIVE_HIGH>;
+               status-gpio = <&gpio4 11 GPIO_ACTIVE_HIGH>;
+       };
-- 
2.7.4

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