Make handling of port disconnection generic.

cmd.c

 		.port_id1 = "serial",
 		.port_id2 = "serial",
 		.opt_prefix = "se",
+		.allow_disconnect = true,
 	},
 	[CMD_SERIAL_PORT_STATUS]  = { .cmd = CMD_SERIAL_PORT_STATUS , .type = PARSE_STATUS,
 		.ports1 = OFS(serial),
 		case PARSE_ROUTE:
 			dest_port_num = strtoul(port_data, NULL, 10);
 			if (dest_port_num == NO_PORT) {
-				// Only serial port routing can be disabled with -1
-				if (v->cmd == CMD_SERIAL_PORT_ROUTING) {
+				if (v->allow_disconnect) {
 					s_port->port[port_num].routed_to = dest_port_num;
 					continue;
 				} else {
 			);
 			break;
 		}
-		if (e->cmd->cmd == CMD_SERIAL_PORT_ROUTING) {
+		if (e->cmd->allow_disconnect) {
 			printf("%sconnect %s %d \"%s\" to %s %d \"%s\"\n",
 				prefix,
 				e->cmd->port_id1,

cmd.h

 	const char		*port_id1;
 	const char		*port_id2;
 	const char		*opt_prefix;
+	bool			allow_disconnect;
 };
 
 extern struct videohub_commands videohub_commands[NUM_COMMANDS];