spi: add driver for NXP XSPI controller

Add driver support for NXP XSPI controller.

XSPI is a flexible SPI host controller which supports up to
2 external devices (2 CS). It support Single/Dual/Quad/Octal
mode data transfer.

The difference between XSPI and Flexspi:
1.the register layout is total different.
2.XSPI support multiple independent execution environments
(EENVs) for HW virtualization with some limitations. Each EENV
has its own interrupt and its own set of programming registers
that exists in a specific offset range in the XSPI memory map.
The main environment (EENV0) address space contains all of the
registers for controlling EENV0 plus all of the general XSPI
control and programming registers. The register mnemonics for
the user environments (EENV1 to EENV4) have "_SUB_n" appended
to the mnemonic for the corresponding main-environment register.

Current driver based on EENV0, which means system already give
EENV0 right to linux.

This driver use SPI memory interface of the SPI framework to
issue flash memory operations. Tested this driver with UBIFS
and mtd_debug on NXP i.MX943 EVK board which has one spi nor
MT35XU512ABA flash. Now this driver has the following key
features:
- Support up to OCT DDR mode
- Support AHB read
- Support IP read and IP write
- Support two CS

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Link: https://patch.msgid.link/20251216-xspi-v7-2-282525220979@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>

MAINTAINERS

@@ -18953,6 +18953,7 @@ L:	linux-spi@vger.kernel.org
 L:	imx@lists.linux.dev
 S:	Maintained
 F:	Documentation/devicetree/bindings/spi/nxp,imx94-xspi.yaml
+F:	drivers/spi/spi-nxp-xspi.c
 
 NXP-NCI NFC DRIVER
 S:	Orphan

drivers/spi/Kconfig

@@ -481,6 +481,16 @@ config SPI_NXP_FLEXSPI
 	  This controller does not support generic SPI messages and only
 	  supports the high-level SPI memory interface.
 
+config SPI_NXP_XSPI
+        tristate "NXP xSPI controller"
+	depends on ARCH_MXC || COMPILE_TEST
+	depends on HAS_IOMEM
+	help
+	  This enables support for the xSPI controller. Up to two devices
+	  can be connected to one host.
+	  This controller does not support generic SPI messages and only
+	  supports the high-level SPI memory interface.
+
 config SPI_GPIO
 	tristate "GPIO-based bitbanging SPI Master"
 	depends on GPIOLIB || COMPILE_TEST

drivers/spi/Makefile

@@ -102,6 +102,7 @@ obj-$(CONFIG_SPI_WPCM_FIU)		+= spi-wpcm-fiu.o
 obj-$(CONFIG_SPI_NPCM_FIU)		+= spi-npcm-fiu.o
 obj-$(CONFIG_SPI_NPCM_PSPI)		+= spi-npcm-pspi.o
 obj-$(CONFIG_SPI_NXP_FLEXSPI)		+= spi-nxp-fspi.o
+obj-$(CONFIG_SPI_NXP_XSPI)		+= spi-nxp-xspi.o
 obj-$(CONFIG_SPI_OC_TINY)		+= spi-oc-tiny.o
 spi-octeon-objs				:= spi-cavium.o spi-cavium-octeon.o
 obj-$(CONFIG_SPI_OCTEON)		+= spi-octeon.o