IIO: Add basic MXS LRADC driver

This driver is very basic. It supports userland trigger, buffer and
raw access to channels. The support for delay channels is missing
altogether.
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Juergen Beisert <jbe@pengutronix.de>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Wolfgang Denk <wd@denx.de>

Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt

+* Freescale i.MX28 LRADC device driver
+
+Required properties:
+- compatible: Should be "fsl,imx28-lradc"
+- reg: Address and length of the register set for the device
+- interrupts: Should contain the LRADC interrupts
+
+Examples:
+
+	lradc@80050000 {
+		compatible = "fsl,imx28-lradc";
+		reg = <0x80050000 0x2000>;
+		interrupts = <10 14 15 16 17 18 19
+				20 21 22 23 24 25>;
+	};

drivers/staging/iio/adc/Kconfig

@@ -200,6 +200,18 @@ config LPC32XX_ADC
 	  activate only one via device tree selection.  Provides direct access
 	  via sysfs.
 
+config MXS_LRADC
+	tristate "Freescale i.MX28 LRADC"
+	depends on ARCH_MXS
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for i.MX28 LRADC convertor
+	  built into these chips.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called mxs-lradc.
+
 config SPEAR_ADC
 	tristate "ST SPEAr ADC"
 	depends on PLAT_SPEAR

drivers/staging/iio/adc/Makefile

@@ -38,4 +38,5 @@ obj-$(CONFIG_ADT7310) += adt7310.o
 obj-$(CONFIG_ADT7410) += adt7410.o
 obj-$(CONFIG_AD7280) += ad7280a.o
 obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
+obj-$(CONFIG_MXS_LRADC) += mxs-lradc.o
 obj-$(CONFIG_SPEAR_ADC) += spear_adc.o