soc/tegra: Implement runtime check for Tegra SoCs

Subsequent patches will move some of the initialization code from SoC
setup code to regular initcalls. To prevent breakage on other SoCs in
multi-platform builds, these initcalls need to check that they indeed
run on Tegra.
Signed-off-by: NThierry Reding <treding@nvidia.com>

drivers/soc/tegra/Makefile

 obj-$(CONFIG_ARCH_TEGRA) += fuse/
+
+obj-$(CONFIG_ARCH_TEGRA) += common.o

drivers/soc/tegra/common.c

+/*
+ * Copyright (C) 2014 NVIDIA CORPORATION.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/of.h>
+
+#include <soc/tegra/common.h>
+
+static const struct of_device_id tegra_machine_match[] = {
+	{ .compatible = "nvidia,tegra20", },
+	{ .compatible = "nvidia,tegra30", },
+	{ .compatible = "nvidia,tegra114", },
+	{ .compatible = "nvidia,tegra124", },
+	{ }
+};
+
+bool soc_is_tegra(void)
+{
+	struct device_node *root;
+
+	root = of_find_node_by_path("/");
+	if (!root)
+		return false;
+
+	return of_match_node(tegra_machine_match, root) != NULL;
+}

include/soc/tegra/common.h

+/*
+ * Copyright (C) 2014 NVIDIA Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __SOC_TEGRA_COMMON_H__
+#define __SOC_TEGRA_COMMON_H__
+
+bool soc_is_tegra(void);
+
+#endif /* __SOC_TEGRA_COMMON_H__ */