ARM i.MX27: Add devicetree support

This patch adds basic devicetree support for i.MX27 based SoCs.
Only the bindings for which drivers exist are added here:

- UART
- fec
- CSPI
- I2C
- watchdog
- gpio

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/arch/arm/mach-imx/clock-imx27.c b/arch/arm/mach-imx/clock-imx27.c
index 88fe00a..01ae3a4 100644
--- a/arch/arm/mach-imx/clock-imx27.c
+++ b/arch/arm/mach-imx/clock-imx27.c
@@ -22,6 +22,7 @@
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/clkdev.h>
+#include <linux/of.h>
 
 #include <asm/div64.h>
 
@@ -764,3 +765,20 @@
 	return 0;
 }
 
+#ifdef CONFIG_OF
+int __init mx27_clocks_init_dt(void)
+{
+	struct device_node *np;
+	u32 fref = 26000000; /* default */
+
+	for_each_compatible_node(np, NULL, "fixed-clock") {
+		if (!of_device_is_compatible(np, "fsl,imx-osc26m"))
+			continue;
+
+		if (!of_property_read_u32(np, "clock-frequency", &fref))
+			break;
+	}
+
+	return mx27_clocks_init(fref);
+}
+#endif