mtd: spi-nor: add the framework for SPI NOR

This patch cloned most of the m25p80.c. In theory, it adds a new spi-nor layer.

Before this patch, the layer is like:

                   MTD
         ------------------------
                  m25p80
         ------------------------
	       spi bus driver
         ------------------------
	        SPI NOR chip

After this patch, the layer is like:
                   MTD
         ------------------------
                  spi-nor
         ------------------------
                  m25p80
         ------------------------
	       spi bus driver
         ------------------------
	       SPI NOR chip

With the spi-nor controller driver(Freescale Quadspi), it looks like:
                   MTD
         ------------------------
                  spi-nor
         ------------------------
                fsl-quadspi
         ------------------------
	       SPI NOR chip

New APIs:
   spi_nor_scan: used to scan a spi-nor flash.
Signed-off-by: Huang Shijie <b32955@freescale.com>
Acked-by: Marek Vasut <marex@denx.de>
[Brian: rebased to include additional m25p_ids[] entry]
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/Kconfig

@@ -321,6 +321,8 @@ source "drivers/mtd/onenand/Kconfig"
 
 source "drivers/mtd/lpddr/Kconfig"
 
+source "drivers/mtd/spi-nor/Kconfig"
+
 source "drivers/mtd/ubi/Kconfig"
 
 endif # MTD

drivers/mtd/Makefile

@@ -32,4 +32,5 @@ inftl-objs		:= inftlcore.o inftlmount.o
 
 obj-y		+= chips/ lpddr/ maps/ devices/ nand/ onenand/ tests/
 
+obj-$(CONFIG_MTD_SPI_NOR_BASE)	+= spi-nor/
 obj-$(CONFIG_MTD_UBI)		+= ubi/

drivers/mtd/spi-nor/Kconfig

+config MTD_SPI_NOR_BASE
+	bool "the framework for SPI-NOR support"
+	depends on MTD
+	help
+	  This is the framework for the SPI NOR which can be used by the SPI
+	  device drivers and the SPI-NOR device driver.

drivers/mtd/spi-nor/Makefile

+obj-$(CONFIG_MTD_SPI_NOR_BASE)	+= spi-nor.o

include/linux/mtd/spi-nor.h

@@ -162,4 +162,24 @@ struct spi_nor {
 
 	void *priv;
 };
+
+/**
+ * spi_nor_scan() - scan the SPI NOR
+ * @nor:	the spi_nor structure
+ * @id:		the spi_device_id provided by the driver
+ * @mode:	the read mode supported by the driver
+ *
+ * The drivers can use this fuction to scan the SPI NOR.
+ * In the scanning, it will try to get all the necessary information to
+ * fill the mtd_info{} and the spi_nor{}.
+ *
+ * The board may assigns a spi_device_id with @id which be used to compared with
+ * the spi_device_id detected by the scanning.
+ *
+ * Return: 0 for success, others for failure.
+ */
+int spi_nor_scan(struct spi_nor *nor, const struct spi_device_id *id,
+			enum read_mode mode);
+extern const struct spi_device_id spi_nor_ids[];
+
 #endif