docs: Tweak Power Mgm run_every description & indicate UART wakeup.

Author: microbit-carlos

docs/power.rst

@@ -9,7 +9,7 @@ There are two micro:bit board low power modes that can be requested from
 MicroPython:
 
 - **Deep Sleep**: Low power mode where the board can be woken up via
-  multiple sources (pins, button presses, or a timer) and resume
+  multiple sources (pins, button presses, uart data, or a timer) and resume
   operation.
 - **Off**: The power mode with the lowest power consumption, the only way to
   wake up the board is via the reset button, or by plugging the USB cable while
@@ -49,15 +49,14 @@ Functions
 
     The wake up sources are configured via arguments.
 
-    If no wake up sources have been configured it will sleep until the reset
+    The board will always wake up when receiving UART data, when the reset
     button is pressed (which resets the board) or, in battery power,
     when the USB cable is inserted.
 
     When the ``run_every`` parameter is set to ``True`` (the default), any
     function scheduled with :py:meth:`microbit.run_every<microbit.run_every>`
-    will still run while the board sleeps. When the scheduled time is reached
-    the micro:bit will momentarily wake up to run the scheduled function
-    and then automatically go back to sleep.
+    will momentarily wake up the board to run and when it finishes it will go
+    back to sleep.
 
     :param ms: A time in milliseconds to wait before it wakes up.
     :param wake_on: A single instance or a tuple of pins and/or buttons to
@@ -130,3 +129,13 @@ the USB connection.
 +------------------+-----------------+--------------------+
 | **Off**          | 📴 Power Down   | 📴 Power Down      |
 +------------------+-----------------+--------------------+
+
+Deep Sleep & run_every
+----------------------
+
+To make sure the :py:meth:`microbit.run_every<microbit.run_every>`
+functions continue to run during "Deep Sleep", the micro:bit will wake up
+at the correct time to run the next scheduled ``run_every``,
+and then go back to "Deep Sleep" mode as soon as that ``run_every`` completes.
+It will continue to do this until the deep sleep finishes due
+to the ``ms`` timeout being reached, or a ``wake_on`` event occurs.