mtd: spi: Add Renesas RPC SPI-flash driver

Add driver for the RPC block in SPI-flash mode. This driver allows
access to a SPI NOR flash attached to the RPC block and does not
support RPC in Hyperflash mode. Note that this block is extremely
selective when communicating with the SPI NOR.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index d3e407e..ec92b84 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -114,6 +114,14 @@
 	  to access the SPI NOR flash, MMC-over-SPI on platforms based on
 	  Microchip PIC32 family devices.
 
+config RENESAS_RPC_SPI
+	bool "Renesas RPC SPI driver"
+	depends on RCAR_GEN3
+	help
+	  Enable the Renesas RPC SPI driver, used to access SPI NOR flash
+	  on Renesas RCar Gen3 SoCs. This uses driver model and requires a
+	  device tree binding to operate.
+
 config ROCKCHIP_SPI
 	bool "Rockchip SPI driver"
 	help