drivers: introduce Meson Secure Monitor driver

This patch adds an implementation of the Meson Secure Monitor
driver based on UCLASS_SM.

Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/r/20230921081346.22157-7-avromanov@salutedevices.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 7d5d053..16b17fd 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -161,6 +161,7 @@
 F:	drivers/adc/meson-saradc.c
 F:	drivers/phy/meson*
 F:	drivers/mmc/meson_gx_mmc.c
+F:	drivers/sm/meson-sm.c
 F:	drivers/spi/meson_spifc.c
 F:	drivers/pinctrl/meson/
 F:	drivers/power/domain/meson-gx-pwrc-vpu.c