Update for supporting multiple logging level settings

articles/150_ros_command_line_arguments.md

@@ -167,16 +167,24 @@ another_node:
      string_param: bar
 ```
 
-#### Logging level
+#### Multiple logging level assignments
 
-Minimum logging level can be externally set using the `--log-level` option.
+Logging level assignments have two means of settings which are a global logging level and other logging levels for specific loggers. Minimum logging level can be externally set using the `--log-level` option.
 
-As an example, to set logging level to `DEBUG` for `some_ros_executable`, one may execute:
+As an example, to set a global logging level to `DEBUG` for `some_ros_executable`, one may execute:
 
 ```sh
 ros2 run some_package some_ros_executable --ros-args --log-level DEBUG
 ```
 
+Some specific loggers can be set using the `--log-level` option as well, the format as follows:
+
+```sh
+ros2 run some_package some_ros_executable --ros-args --log-level talker1:=DEBUG --log-level talker2:=WARN
+```
+
+Note that the logging level of a specific logger can override the global logging level for this logger.
+
 See `rcutils` and `rcl` logging documentation for reference on existing logging levels.
 
 #### External logging configuration