dm: MIGRATION: Add migration plan for DM_USB

As much of the USB system has been migrated to DM now, formalize a
deadline for migration.

Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/doc/driver-model/MIGRATION.txt b/doc/driver-model/MIGRATION.txt
index 71c2657..0b763f7 100644
--- a/doc/driver-model/MIGRATION.txt
+++ b/doc/driver-model/MIGRATION.txt
@@ -15,6 +15,16 @@
 switching over to using CONFIG_DM_MMC and other base driver model options in
 time for inclusion in the 2019.04 rerelease.
 
+CONFIG_DM_USB
+-------------
+
+Status: In progress
+Deadline: 2019.07
+
+The subsystem itself has been converted along with many of the host controller
+and maintainers should submit patches switching over to using CONFIG_DM_USB and
+other base driver model options in time for inclusion in the 2019.07 rerelease.
+
 CONFIG_BLK
 ----------