spi_flash: Add spi_flash_probe_fdt() to locate SPI by FDT node

This allows us to put the SPI flash chip inside the SPI interface node,
with U-Boot finding the correct bus and chip select automatically.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/spi.h b/include/spi.h
index e2563c9..aba7922 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -259,13 +259,24 @@
  * spi_free_slave() to free it later.
  *
  * @param blob:		Device tree blob
- * @param node:		SPI peripheral node to use
- * @param cs:		Chip select to use
- * @param max_hz:	Maximum SCK rate in Hz (0 for default)
- * @param mode:		Clock polarity, clock phase and other parameters
+ * @param slave_node:	Slave node to use
+ * @param spi_node:	SPI peripheral node to use
  * @return pointer to new spi_slave structure
  */
-struct spi_slave *spi_setup_slave_fdt(const void *blob, int node,
-		unsigned int cs, unsigned int max_hz, unsigned int mode);
+struct spi_slave *spi_setup_slave_fdt(const void *blob, int slave_node,
+				      int spi_node);
+
+/**
+ * spi_base_setup_slave_fdt() - helper function to set up a SPI slace
+ *
+ * This decodes SPI properties from the slave node to determine the
+ * chip select and SPI parameters.
+ *
+ * @blob:	Device tree blob
+ * @busnum:	Bus number to use
+ * @node:	Device tree node for the SPI bus
+ */
+struct spi_slave *spi_base_setup_slave_fdt(const void *blob, int busnum,
+					   int node);
 
 #endif	/* _SPI_H_ */