MAINTAINERS: Add GPIO Aggregator section

Add a maintainership section for the GPIO Aggregator, covering
documentation and driver source code.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Link: https://lore.kernel.org/r/20200511145257.22970-7-geert+renesas@glider.beSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -7228,6 +7228,13 @@ F:	Documentation/firmware-guide/acpi/gpio-properties.rst
 F:	drivers/gpio/gpiolib-acpi.c
 F:	drivers/gpio/gpiolib-acpi.h
 
+GPIO AGGREGATOR
+M:	Geert Uytterhoeven <geert+renesas@glider.be>
+L:	linux-gpio@vger.kernel.org
+S:	Supported
+F:	Documentation/admin-guide/gpio/gpio-aggregator.rst
+F:	drivers/gpio/gpio-aggregator.c
+
 GPIO IR Transmitter
 M:	Sean Young <sean@mess.org>
 L:	linux-media@vger.kernel.org