mfd: Add syscon driver based on regmap

Add regmap based syscon driver.
This is usually used for access misc bits in registers which does not belong
to a specific module, for example, IMX IOMUXC GPR and ANATOP.
With this driver, client can use generic regmap API to access registers
which are registered into syscon.

Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

include/linux/mfd/syscon.h

@@ -0,0 +1,23 @@
+/*
+ * System Control Driver
+ *
+ * Copyright (C) 2012 Freescale Semiconductor, Inc.
+ * Copyright (C) 2012 Linaro Ltd.
+ *
+ * Author: Dong Aisheng <dong.aisheng@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef __LINUX_MFD_SYSCON_H__
+#define __LINUX_MFD_SYSCON_H__
+
+extern struct regmap *syscon_node_to_regmap(struct device_node *np);
+extern struct regmap *syscon_regmap_lookup_by_compatible(const char *s);
+extern struct regmap *syscon_regmap_lookup_by_phandle(
+					struct device_node *np,
+					const char *property);
+#endif /* __LINUX_MFD_SYSCON_H__ */