rockchip: Add MAINTAINERS entry for Radxa Rock 4C+

This defconfig was added without a MAINTAINERS entry, add one.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/board/rockchip/evb_rk3399/MAINTAINERS b/board/rockchip/evb_rk3399/MAINTAINERS
index 5be58f8..de1dc64 100644
--- a/board/rockchip/evb_rk3399/MAINTAINERS
+++ b/board/rockchip/evb_rk3399/MAINTAINERS
@@ -80,6 +80,12 @@
 F:	arch/arm/dts/rk3399-u-boot.dtsi
 F:	arch/arm/dts/rk3399-orangepi-u-boot.dtsi
 
+RADXA ROCK 4C+
+M:	FUKAUMI Naoki <naoki@radxa.com>
+S:	Maintained
+F:	configs/rock-4c-plus-rk3399_defconfig
+F:	arch/arm/dts/rk3399-rock-4c-plus.dts
+
 ROCK-PI-4
 M:	Akash Gajjar <akash@openedev.com>
 M:	Jagan Teki <jagan@amarulasolutions.com>