The basic firmware is written by the chip manufacturer (Broadcom in this case), but router manufacturers customise the firmware in various ways. Netgear routers, for example, use 'adslctl' instead of the normal 'adsl', and the HG612 uses 'xdslcmd'. Thomson/Speedtouch/Technicolour hide the Broadcom CLI completely by wrapping it in their own own interface which uses different commands.
But as far as I know, all Broadcom-based routers which offer full access to the Broadcom CLI use the same command parameters for tweaking the SNRM, i.e. <command prefix> configure --snr N. So you only have three varieties of the command to cater for. But in addition you have to allow for the fact that some routers, such as the HG612, require an extra command to be entered after logging into the router, to get to the BusyBox shell with the Broadcom commands.