From https://github.com/torvalds/linux/blob/master/include/uapi/linux/input-event-codes.h,
KEY_SUBTITLE is near the TV codes. Note that 0x172 == 370.
#define KEY_CHANNEL 0x16b
#define KEY_FAVORITES 0x16c
#define KEY_EPG 0x16d
#define KEY_PVR 0x16e /* Media Select Home */
#define KEY_MHP 0x16f
#define KEY_LANGUAGE 0x170
#define KEY_TITLE 0x171
#define KEY_SUBTITLE 0x172
#define KEY_ANGLE 0x173
#define KEY_FULL_SCREEN 0x174 /* AC View Toggle */
#define KEY_ZOOM KEY_FULL_SCREEN
You can also see on https://www.kernel.org/doc/html/v4.9/media/uapi/rc/rc-tables.html it is listed in the "Movie play control" section:
KEY_SUBTITLE Allow changing the subtitle
Change-Id: I7690269cddd00b787a939f87ba651db38f1160ac
Signed-off-by: Aman Gupta <aman@tmm1.net>
6c984953ea