[ADD] Point of Sale: New doc about fiscal positions (#603)

point_of_sale/restaurant.rst

@@ -12,4 +12,5 @@ Restaurant Features
    restaurant/kitchen_printing
    restaurant/tips
    restaurant/transfer
-   restaurant/multi_orders
+   restaurant/multi_orders
+   restaurant/fiscal_position

point_of_sale/restaurant/fiscal_position.rst

@@ -0,0 +1,43 @@
+=============================
+Using fiscal positions in PoS
+=============================
+
+In Odoo, *Fiscal Positions* let you apply different taxes based on
+the customer location. In a *Point of Sale*, such as a restaurant, it can
+be used to apply different taxes depending if the customer eats in or
+takes away.
+
+Set up fiscal positions for PoS
+===============================
+
+To enable this feature, go to :menuselection:`Point of Sale --> Configuration --> Point of Sale` 
+and check *Fiscal Position per Order*. Now, you can choose the fiscal positions
+you want for your *PoS*.
+
+.. image:: media/fiscal_position_01.png
+    :align: center
+
+.. note::
+   You need to create your fiscal positions before using this feature.
+
+Using fiscal positions
+======================
+
+Once on your *PoS* interface, click on the *Tax* button.
+Now, choose the fiscal position you need for the current order.
+
+.. image:: media/fiscal_position_02.png
+    :align: center
+
+Set up a default fiscal position
+================================
+
+If you want to use a default fiscal position, meaning that a preexisting value is always 
+automatically assigned, go to :menuselection:`Point of Sale --> Configuration 
+--> Point of Sale` and enable *Fiscal Position*. Now, choose one to set as the default one.
+
+.. image:: media/fiscal_position_03.png
+    :align: center
+
+.. note::
+   Now, the *tax* button is replaced by a *on site* button when on the *PoS* interface.