1ARM PL022 SPI controller
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3Required properties:
4- compatible : "arm,pl022", "arm,primecell"
5- reg : Offset and length of the register set for the device
6- interrupts : Should contain SPI controller interrupt
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8Optional properties:
9- cs-gpios : should specify GPIOs used for chipselects.
10  The gpios will be referred to as reg = <index> in the SPI child nodes.
11  If unspecified, a single SPI device without a chip select can be used.
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