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_flash.h b/include/spi_flash.h
index 25ca8f1..afc3a58 100644
--- a/include/spi_flash.h
+++ b/include/spi_flash.h
@@ -67,6 +67,19 @@
 
 struct spi_flash *spi_flash_probe(unsigned int bus, unsigned int cs,
 		unsigned int max_hz, unsigned int spi_mode);
+
+/**
+ * Set up a new SPI flash from an fdt node
+ *
+ * @param blob		Device tree blob
+ * @param slave_node	Pointer to this SPI slave node in the device tree
+ * @param spi_node	Cached pointer to the SPI interface this node belongs
+ *			to
+ * @return 0 if ok, -1 on error
+ */
+struct spi_flash *spi_flash_probe_fdt(const void *blob, int slave_node,
+				      int spi_node);
+
 void spi_flash_free(struct spi_flash *flash);
 
 static inline int spi_flash_read(struct spi_flash *flash, u32 offset,