soc: apple: Add DockChannel driver

DockChannel is a simple FIFO interface used to communicate between SoC
blocks. Add a driver that represents the shared interrupt controller for
the DockChannel block, and then exposes probe and data transfer
functions that child device drivers can use to instantiate individual
FIFOs.

Signed-off-by: Hector Martin <marcan@marcan.st>

Author: marcan

drivers/soc/apple/Kconfig

@@ -4,6 +4,15 @@ if ARCH_APPLE || COMPILE_TEST
 
 menu "Apple SoC drivers"
 
+config APPLE_DOCKCHANNEL
+	tristate "Apple DockChannel FIFO"
+	depends on ARCH_APPLE || COMPILE_TEST
+	help
+	  DockChannel is a simple FIFO used on Apple SoCs for debug and inter-processor
+	  communications.
+
+	  Say 'y' here if you have an Apple SoC.
+
 config APPLE_MAILBOX
 	tristate "Apple SoC mailboxes"
 	depends on PM

drivers/soc/apple/Makefile

@@ -1,5 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
+obj-$(CONFIG_APPLE_DOCKCHANNEL) += apple-dockchannel.o
+apple-dockchannel-y = dockchannel.o
+
 obj-$(CONFIG_APPLE_MAILBOX) += apple-mailbox.o
 apple-mailbox-y = mailbox.o