On Thu, Nov 02, 2017 at 04:42:56PM +0100, Paul Menzel wrote:

The Linux serial console documentation [1] says that 115200 is the maximum
supported baudrate.

quoted

The maximum baudrate is 115200.

Is that still accurate? If yes, where should I look to support higher
values?

See the setserial man page and the spd_* options:

spd_hi
    Use 57.6kb when the application requests 38.4kb. This parameter
    may be specified by a non-privileged user.
     
spd_vhi
    Use 115kb when the application requests 38.4kb. This parameter may
    be specified by a non-privileged user.
    
spd_shi
    Use 230kb when the application requests 38.4kb. This parameter may
    be specified by a non-privileged user.

spd_warp
    Use 460kb when the application requests 38.4kb. This parameter may
    be specified by a non-privileged user.

						- Ted