sensor_monitor: add /proc/sensor_monitor

  "Sensor procfs - Dynamic sensor debugging tool\n"
  "\n"
  "Usage:\n"
  "  cat /proc/sensor_monitor - Show currently monitored topics\n"
  "  echo <level> <topic> > /proc/sensor_monitor - Add topic(s)\n"
  "  echo rm <topic> > /proc/sensor_monitor - Remove topic(s)\n"
  "  echo add <topic> <topic> > /proc/sensor_monitor"
  " - add/remove topics\n"
  "  echo clean > /proc/sensor_monitor      - Remove all topics\n"
  "\n"
  "Examples:\n"
  "  echo sensor_accel > /proc/sensor_monitor\n"
  "  echo \"sensor_accel sensor_compass\" > /proc/sensor_monitor\n"
  "  echo \"1 sensor_accel sensor_compass\" > /proc/sensor_monitor\n"
  "  echo \"2 sensor_accel sensor_compass\" > /proc/sensor_monitor\n"
  "  echo \"rm sensor_accel\" > /proc/sensor_monitor\n"
  "  echo \"rm sensor_accel sensor_compass\" > /proc/sensor_monitor\n"
  "  echo clean > /proc/sensor_monitor\n"
  "  echo \"add 1 sensor_a rm sensor_b\" > /proc/sensor_monitor\n"
  "\n"
  "Note:\n"
  "  If <level> is not specified, it defaults to 1.\n";

Signed-off-by: chenzihan1 <chenzihan1@xiaomi.com>

Author: chenzihan0416

Documentation/components/drivers/special/sensors.rst

@@ -10,11 +10,15 @@ Currently in NuttX we have 3 different approaches to sensor interfaces:
     sensors/sensors_uorb.rst
     sensors/sensors_legacy.rst
     sensors/sensors_cluster.rst
+    sensors/sensor_monitor.rst
 
 The preferred way for implementing new sensors is
 the :ref:`New sensor framework <new_sensor_framework>`, which provides the most
 general interface.
 
+The :doc:`Sensor Monitor <sensors/sensor_monitor>` provides a dynamic debugging
+tool for monitoring sensor activity at runtime.
+
 .. attach files to avoid warnings, but don't show them here !
 
 .. toctree::