dm: Add support for generic system controllers (syscon)

Many SoCs have a number of system controllers which are dealt with as a
group by a single driver. It is a pain to have to add lots of compatible
strings and/or separate drivers for each. Instead we can identify the
controllers by a number and request the address of the one we want.

Add a simple implementation of this which can be used by SoC driver code.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/syscon.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __SYSCON_H
+#define __SYSCON_H
+
+/**
+ * struct syscon_uc_info - Information stored by the syscon UCLASS_UCLASS
+ *
+ * @regmap:	Register map for this controller
+ */
+struct syscon_uc_info {
+	struct regmap *regmap;
+};
+
+/* So far there are no ops so this is a placeholder */
+struct syscon_ops {
+};
+
+#define syscon_get_ops(dev)        ((struct syscon_ops *)(dev)->driver->ops)
+
+/**
+ * syscon_get_regmap() - Get access to a register map
+ *
+ * @dev:	Device to check (UCLASS_SCON)
+ * @info:	Returns regmap for the device
+ * @return 0 if OK, -ve on error
+ */
+struct regmap *syscon_get_regmap(struct udevice *dev);
+
+/**
+ * syscon_get_regmap_by_driver_data() - Look up a controller by its ID
+ *
+ * Each system controller can be accessed by its driver data, which is
+ * assumed to be unique through the scope of all system controllers that
+ * are in use. This function looks up the regmap given this driver data.
+ *
+ * @driver_data:	Driver data value to look up
+ * @return register map correponding to @driver_data, or -ve error code
+ */
+struct regmap *syscon_get_regmap_by_driver_data(ulong driver_data);
+
+/**
+ * syscon_get_first_range() - get the first memory range from a syscon regmap
+ *
+ * @driver_data:	Driver data value to look up
+ * @return first region of register map correponding to @driver_data, or
+ *			-ve error code
+ */
+void *syscon_get_first_range(ulong driver_data);
+
+#endif