ASoC: pxa: add DT bindings for pxa2xx-pcm

The bindings do not carry any resources, as the module only registers
the ASoC platform driver.
Signed-off-by: NDaniel Mack <zonque@gmail.com>
Signed-off-by: NMark Brown <broonie@linaro.org>

Documentation/devicetree/bindings/sound/mrvl,pxa2xx-pcm.txt

+DT bindings for ARM PXA2xx PCM platform driver
+
+This is just a dummy driver that registers the PXA ASoC platform driver.
+It does not have any resources assigned.
+
+Required properties:
+
+	- compatible		'mrvl,pxa-pcm-audio'
+
+Example:
+
+	pxa_pcm_audio: snd_soc_pxa_audio {
+		compatible = "mrvl,pxa-pcm-audio";
+	};
+

sound/soc/pxa/pxa2xx-pcm.c

@@ -13,6 +13,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/module.h>
 #include <linux/dmaengine.h>
+#include <linux/of.h>
 
 #include <sound/core.h>
 #include <sound/soc.h>
@@ -133,10 +134,18 @@ static int pxa2xx_soc_platform_remove(struct platform_device *pdev)
 	return 0;
 }
 
+#ifdef CONFIG_OF
+static const struct of_device_id snd_soc_pxa_audio_match[] = {
+	{ .compatible   = "mrvl,pxa-pcm-audio" },
+	{ }
+};
+#endif
+
 static struct platform_driver pxa_pcm_driver = {
 	.driver = {
-			.name = "pxa-pcm-audio",
-			.owner = THIS_MODULE,
+		.name = "pxa-pcm-audio",
+		.owner = THIS_MODULE,
+		.of_match_table = of_match_ptr(snd_soc_pxa_audio_match),
 	},
 
 	.probe = pxa2xx_soc_platform_probe,