spi: add support for microchip "soft" spi controller

Introduce driver support for the Microchip FPGA CoreSPI IP.

This driver supports only Motorola SPI mode and frame size of 8-bits.
TI/NSC modes and wider frame sizes are not currently supported.

Signed-off-by: Prajna Rajendra Kumar <prajna.rajendrakumar@microchip.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20251114104545.284765-4-prajna.rajendrakumar@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: prajnark

drivers/spi/Kconfig

@@ -715,6 +715,15 @@ config SPI_MICROCHIP_CORE_QSPI
 	  PolarFire SoC.
 	  If built as a module, it will be called spi-microchip-core-qspi.
 
+config SPI_MICROCHIP_CORE_SPI
+	tristate "Microchip FPGA CoreSPI controller"
+	depends on SPI_MASTER
+	help
+	  This enables the SPI driver for Microchip FPGA CoreSPI controller.
+	  Say Y or M here if you want to use the "soft" controllers on
+	  PolarFire SoC.
+	  If built as a module, it will be called spi-microchip-core-spi.
+
 config SPI_MT65XX
 	tristate "MediaTek SPI controller"
 	depends on ARCH_MEDIATEK || COMPILE_TEST

drivers/spi/Makefile

@@ -87,6 +87,7 @@ obj-$(CONFIG_SPI_LP8841_RTC)		+= spi-lp8841-rtc.o
 obj-$(CONFIG_SPI_MESON_SPICC)		+= spi-meson-spicc.o
 obj-$(CONFIG_SPI_MESON_SPIFC)		+= spi-meson-spifc.o
 obj-$(CONFIG_SPI_MICROCHIP_CORE_QSPI)	+= spi-microchip-core-qspi.o
+obj-$(CONFIG_SPI_MICROCHIP_CORE_SPI)	+= spi-microchip-core-spi.o
 obj-$(CONFIG_SPI_MPC512x_PSC)		+= spi-mpc512x-psc.o
 obj-$(CONFIG_SPI_MPC52xx_PSC)		+= spi-mpc52xx-psc.o
 obj-$(CONFIG_SPI_MPC52xx)		+= spi-mpc52xx.o