MAINTAINERS: add an entry for StarFive devicetrees

Emil looks after the downstream StarFive stuff, and agreed to look after
the upstream ones too.

CC: Emil Renner Berthing <kernel@esmil.dk>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Emil Renner Berthing <kernel@esmil.dk>
Link: https://lore.kernel.org/r/20221109212219.1598355-4-conor@kernel.orgSigned-off-by: Arnd Bergmann <arnd@arndb.de>

MAINTAINERS

@@ -19626,6 +19626,11 @@ M:	Ion Badulescu <ionut@badula.org>
 S:	Odd Fixes
 F:	drivers/net/ethernet/adaptec/starfire*
 
+STARFIVE DEVICETREES
+M:	Emil Renner Berthing <kernel@esmil.dk>
+S:	Maintained
+F:	arch/riscv/boot/dts/starfive/
+
 STARFIVE JH7100 CLOCK DRIVERS
 M:	Emil Renner Berthing <kernel@esmil.dk>
 S:	Maintained