mfd: Add support for UP board CPLD/FPGA

The UP Squared board <http://www.upboard.com> implements certain
features (pin control, onboard LEDs or CEC) through an on-board CPLD/FPGA.

This mfd driver implements the line protocol to read and write registers
from the FPGA through regmap. The register address map is also included.

The UP Boards provide a few I/O pin headers (for both GPIO and
functions), including a 40-pin Raspberry Pi compatible header.

This patch implements support for the FPGA-based pin controller that
manages direction and enable state for those header pins.

Partial support UP boards:
* UP core + CREX
* UP core + CRST02

PATCH V2:
(1) Synchronizing upboard github to rc2
(2) Refer 2022/10/31 Lee Jones review, fixed some of the issues.

Signed-off-by: Javier Arteaga <javier@emutex.com>
[merge various fixes]
Signed-off-by: Nicola Lunghi <nicola.lunghi@emutex.com>
Signed-off-by: chengwei <larry.lai@yunjingtech.com>

drivers/mfd/Kconfig

@@ -2153,6 +2153,18 @@ config MFD_QCOM_PM8008
 	  under it in the device tree. Additional drivers must be enabled in
 	  order to use the functionality of the device.
 
+config MFD_UPBOARD_FPGA
+	tristate "Support for the UP board FPGA"
+	select MFD_CORE
+	depends on X86 && ACPI
+	help
+	  Select this option to enable the Intel AAEON UP and UP^2 on-board FPGA.
+	  The UP board implements certain features (pin control, onboard LEDs or
+	  CEC) through an on-board FPGA.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called upboard-fpga.
+
 menu "Multimedia Capabilities Port drivers"
 	depends on ARCH_SA1100
 

drivers/mfd/Makefile

@@ -251,6 +251,7 @@ obj-$(CONFIG_MFD_ALTERA_A10SR)	+= altera-a10sr.o
 obj-$(CONFIG_MFD_ALTERA_SYSMGR) += altera-sysmgr.o
 obj-$(CONFIG_MFD_STPMIC1)	+= stpmic1.o
 obj-$(CONFIG_MFD_SUN4I_GPADC)	+= sun4i-gpadc.o
+obj-$(CONFIG_MFD_UPBOARD_FPGA)	+= upboard-fpga.o
 
 obj-$(CONFIG_MFD_STM32_LPTIMER)	+= stm32-lptimer.o
 obj-$(CONFIG_MFD_STM32_TIMERS) 	+= stm32-timers.o