ffmpeg -layouts

returns:

Individual channels:
NAME           DESCRIPTION
FL             front left
FR             front right
FC             front center
LFE            low frequency
BL             back left
BR             back right
FLC            front left-of-center
FRC            front right-of-center
BC             back center
SL             side left
SR             side right
TC             top center
TFL            top front left
TFC            top front center
TFR            top front right
TBL            top back left
TBC            top back center
TBR            top back right
DL             downmix left
DR             downmix right
WL             wide left
WR             wide right
SDL            surround direct left
SDR            surround direct right
LFE2           low frequency 2
TSL            top side left
TSR            top side right
BFC            bottom front center
BFL            bottom front left
BFR            bottom front right

Standard channel layouts:
NAME           DECOMPOSITION
mono           FC
stereo         FL+FR
2.1            FL+FR+LFE
3.0            FL+FR+FC
3.0(back)      FL+FR+BC
4.0            FL+FR+FC+BC
quad           FL+FR+BL+BR
quad(side)     FL+FR+SL+SR
3.1            FL+FR+FC+LFE
5.0            FL+FR+FC+BL+BR
5.0(side)      FL+FR+FC+SL+SR
4.1            FL+FR+FC+LFE+BC
5.1            FL+FR+FC+LFE+BL+BR
5.1(side)      FL+FR+FC+LFE+SL+SR
6.0            FL+FR+FC+BC+SL+SR
6.0(front)     FL+FR+FLC+FRC+SL+SR
hexagonal      FL+FR+FC+BL+BR+BC
6.1            FL+FR+FC+LFE+BC+SL+SR
6.1(back)      FL+FR+FC+LFE+BL+BR+BC
6.1(front)     FL+FR+LFE+FLC+FRC+SL+SR
7.0            FL+FR+FC+BL+BR+SL+SR
7.0(front)     FL+FR+FC+FLC+FRC+SL+SR
7.1            FL+FR+FC+LFE+BL+BR+SL+SR
7.1(wide)      FL+FR+FC+LFE+BL+BR+FLC+FRC
7.1(wide-side) FL+FR+FC+LFE+FLC+FRC+SL+SR
7.1(top)       FL+FR+FC+LFE+BL+BR+TFL+TFR
octagonal      FL+FR+FC+BL+BR+BC+SL+SR
cube           FL+FR+BL+BR+TFL+TFR+TBL+TBR
hexadecagonal  FL+FR+FC+BL+BR+BC+SL+SR+TFL+TFC+TFR+TBL+TBC+TBR+WL+WR
downmix        DL+DR
22.2           FL+FR+FC+LFE+BL+BR+FLC+FRC+BC+SL+SR+TC+TFL+TFC+TFR+TBL+TBC+TBR+LFE2+TSL+TSR+BFC+BFL+BFR

https://trac.ffmpeg.org/wiki/AudioChannelManipulation#Listchannelnamesandstandardchannellayouts