Stepper combine lambda docs (#223)

## Description:
#222 

**Related issue (if applicable):** fixes <link to issue>

**Pull request in [esphome](https://github.com/esphome/esphome) with YAML changes (if applicable):** esphome/esphome#<esphome PR number goes here>
**Pull request in [esphome-core](https://github.com/esphome/esphome-core) with C++ framework changes (if applicable):** esphome/esphome-core#<esphome-core PR number goes here>

## Checklist:

  - [x] Branch: `next` is for changes and new documentation that will go public with the next ESPHome release. Fixes, changes and adjustments for the current release should be created against `current`.


Co-authored-by: Otto Winter <otto@otto-winter.com>

components/stepper/index.rst

@@ -155,17 +155,6 @@ Configuration options:
                 id: my_stepper
                 target: 150
 
-.. note::
-
-    This action can also be expressed as a :ref:`lambda <config-lambda>`:
-
-    .. code-block:: cpp
-
-        id(my_stepper).set_target(250);
-
-        // Get the currently set target position:
-        int target = id(my_stepper).target_position;
-
 .. _stepper-report_position_action:
 
 ``stepper.report_position`` Action
@@ -206,17 +195,6 @@ Configuration options:
 - **id** (**Required**, :ref:`config-id`): The ID of the stepper.
 - **target** (*Optional*, int, :ref:`templatable <config-templatable>`): The target position in steps.
 
-.. note::
-
-    This action can also be expressed as a :ref:`lambda <config-lambda>`:
-
-    .. code-block:: cpp
-
-        id(my_stepper).report_position(250);
-
-        // Get the current position:
-        int pos = id(my_stepper).current_position;
-
 .. _stepper-ha-config:
 
 Home Assistant Configuration
@@ -268,6 +246,41 @@ be able to control the stepper from the frontend.
         # [...] stepper config
         id: my_stepper
 
+.. _stepper-lambda_calls:
+
+lambda calls
+------------
+
+From :ref:`lambdas <config-lambda>`, you can call several methods on stepper motors to do some
+advanced stuff (see the full API Reference for more info).
+
+- ``set_target``: Set the target postion of the motor as an integer.
+
+    .. code-block:: cpp
+
+        // Argument is integer (signed int)
+        // Set the (absolute) target position to 250 steps
+        id(my_stepper).set_target(250);
+
+- ``report_position``: Report the current postion as an integer.
+
+    .. code-block:: cpp
+
+        // Report the (absolute) current position as 250 steps
+        id(my_stepper).report_position(250);
+
+- ``current_postion``: Get the current postion of the stepper as an integer.
+
+    .. code-block:: cpp
+
+        int pos = id(my_stepper).current_position;
+
+
+- ``target_position``: Get the set target postion of the stepper  as an integer.
+
+    .. code-block:: cpp
+
+        int pos = id(my_stepper).target_position;
 
 See Also
 --------