drivers: mfd: add class skeleton

Introduce the skeleton for multi-function device drivers. This driver
class is inspired by the same class found in Linux. Multi-function
devices expose multiple functionalities, for example, a LED driver,
regulator, GPIO controller, etc. The MFD driver class serves as a kind
of "parent" device where common functionality can be managed: bus
access, IRQ sharing, initialization code, etc.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

drivers/CMakeLists.txt

@@ -48,6 +48,7 @@ add_subdirectory_ifdef(CONFIG_LORA lora)
 add_subdirectory_ifdef(CONFIG_MBOX mbox)
 add_subdirectory_ifdef(CONFIG_MDIO mdio)
 add_subdirectory_ifdef(CONFIG_MEMC memc)
+add_subdirectory_ifdef(CONFIG_MFD mfd)
 add_subdirectory_ifdef(CONFIG_MIPI_DSI mipi_dsi)
 add_subdirectory_ifdef(CONFIG_MM_DRV mm)
 add_subdirectory_ifdef(CONFIG_MODEM modem)

drivers/Kconfig

@@ -47,6 +47,7 @@ source "drivers/lora/Kconfig"
 source "drivers/mbox/Kconfig"
 source "drivers/mdio/Kconfig"
 source "drivers/memc/Kconfig"
+source "drivers/mfd/Kconfig"
 source "drivers/mipi_dsi/Kconfig"
 source "drivers/misc/Kconfig"
 source "drivers/mm/Kconfig"

drivers/mfd/CMakeLists.txt

@@ -0,0 +1,4 @@
+# Copyright 2023 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_library()

drivers/mfd/Kconfig

@@ -0,0 +1,21 @@
+# Copyright 2023 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+menuconfig MFD
+	bool "Multi-function device (MFD) drivers"
+	help
+	  Include drivers for multi-function devices
+
+if MFD
+
+module = MFD
+module-str = mfd
+source "subsys/logging/Kconfig.template.log_config"
+
+config MFD_INIT_PRIORITY
+	int "Initialization priority"
+	default 60
+	help
+	  Multi-function devices initialization priority.
+
+endif # MFD