spi: add common fdt SPI driver interface

Add a common interface to fdt based SPI drivers.  Each driver is
represented by a table entry in fdt_spi_drivers[].  If there are
multiple SPI drivers in the table, the first driver to return success
from spi_init() will be registered as the SPI driver.

Signed-off-by: Allen Martin <amartin@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
diff --git a/arch/arm/include/asm/arch-tegra20/tegra20_slink.h b/arch/arm/include/asm/arch-tegra20/tegra20_slink.h
index fe8b534..5aa74dd 100644
--- a/arch/arm/include/asm/arch-tegra20/tegra20_slink.h
+++ b/arch/arm/include/asm/arch-tegra20/tegra20_slink.h
@@ -27,4 +27,15 @@
 
 #include <asm/types.h>
 
+int tegra30_spi_init(int *node_list, int count);
+int tegra30_spi_cs_is_valid(unsigned int bus, unsigned int cs);
+struct spi_slave *tegra30_spi_setup_slave(unsigned int bus, unsigned int cs,
+				  unsigned int max_hz, unsigned int mode);
+void tegra30_spi_free_slave(struct spi_slave *slave);
+int tegra30_spi_claim_bus(struct spi_slave *slave);
+void tegra30_spi_cs_activate(struct spi_slave *slave);
+void tegra30_spi_cs_deactivate(struct spi_slave *slave);
+int tegra30_spi_xfer(struct spi_slave *slave, unsigned int bitlen,
+		     const void *data_out, void *data_in, unsigned long flags);
+
 #endif	/* _TEGRA30_SPI_H_ */