spi: npcm-fiu: add NPCM FIU controller driver

Add Nuvoton NPCM BMC Flash Interface Unit(FIU) SPI master
controller driver using SPI-MEM interface.

The FIU supports single, dual or quad communication interface.

the FIU controller can operate in following modes:
- User Mode Access(UMA): provides flash access by using an
  indirect address/data mechanism.
- direct rd/wr mode: maps the flash memory into the core
  address space.
- SPI-X mode: used for an expansion bus to an ASIC or CPLD.
Signed-off-by: NTomer Maimon <tmaimon77@gmail.com>
Link: https://lore.kernel.org/r/20190828142513.228556-3-tmaimon77@gmail.comSigned-off-by: NMark Brown <broonie@kernel.org>

drivers/spi/Kconfig

@@ -433,6 +433,16 @@ config SPI_MT7621
 	help
 	  This selects a driver for the MediaTek MT7621 SPI Controller.
 
+config SPI_NPCM_FIU
+	tristate "Nuvoton NPCM FLASH Interface Unit"
+	depends on ARCH_NPCM || COMPILE_TEST
+	depends on OF && HAS_IOMEM
+	help
+	  This enables support for the Flash Interface Unit SPI controller
+	  in master mode.
+	  This driver does not support generic SPI. The implementation only
+	  supports spi-mem interface.
+
 config SPI_NPCM_PSPI
 	tristate "Nuvoton NPCM PSPI Controller"
 	depends on ARCH_NPCM || COMPILE_TEST

drivers/spi/Makefile

@@ -63,6 +63,7 @@ obj-$(CONFIG_SPI_MT65XX)                += spi-mt65xx.o
 obj-$(CONFIG_SPI_MT7621)		+= spi-mt7621.o
 obj-$(CONFIG_SPI_MXIC)			+= spi-mxic.o
 obj-$(CONFIG_SPI_MXS)			+= spi-mxs.o
+obj-$(CONFIG_SPI_NPCM_FIU)		+= spi-npcm-fiu.o
 obj-$(CONFIG_SPI_NPCM_PSPI)		+= spi-npcm-pspi.o
 obj-$(CONFIG_SPI_NUC900)		+= spi-nuc900.o
 obj-$(CONFIG_SPI_NXP_FLEXSPI)		+= spi-nxp-fspi.o