Man pages matching name tcl_createchannelhandler in section 3tcl:

Tcl_CreateChannelHandler.3tcl.en	debian 10 / tcl8.6-doc
Tcl_CreateChannelHandler.3tcl.en	debian 11 / tcl8.6-doc
Tcl_CreateChannelHandler.3tcl.en	debian 12 / tcl8.6-doc