dm: i2c: Add a migration method for I2C

This probably should have been done a while back since it is a core
system. Add a migration deadline of later this year, to catch the
stragglers.
Signed-off-by: NSimon Glass <sjg@chromium.org>

Makefile

@@ -1096,6 +1096,7 @@ endif
 	$(call deprecated,CONFIG_WDT,DM watchdog,v2019.10,\
 		$(CONFIG_WATCHDOG)$(CONFIG_HW_WATCHDOG))
 	$(call deprecated,CONFIG_DM_ETH,Ethernet drivers,v2020.07,$(CONFIG_NET))
+	$(call deprecated,CONFIG_DM_I2C,I2C drivers,v2022.04,$(CONFIG_I2C))
 	@# Check that this build does not use CONFIG options that we do not
 	@# know about unless they are in Kconfig. All the existing CONFIG
 	@# options are whitelisted, so new ones should not be added.

doc/driver-model/migration.rst

@@ -99,3 +99,11 @@ Deadline: 2020.07
 The network subsystem has supported the driver model since early 2015.
 Maintainers should submit patches switching over to using CONFIG_DM_ETH and
 other base driver model options in time for inclusion in the 2020.07 release.
+
+CONFIG_DM_I2C
+-------------
+Deadline: 2021.10
+
+The I2C subsystem has supported the driver model since early 2015.
+Maintainers should submit patches switching over to using CONFIG_DM_I2C and
+other base driver model options in time for inclusion in the 2021.10 release.