imp board: add blind/buried vias

imp-board.rst

@@ -17,10 +17,11 @@ lower fill order will get filled first. To override the connection style (solid
 Vias
 ----
 
-To place a via while routing, press :kbd:`v`. The "Layer pairs" rule defines which layer the router switches to. To change the size of vias, define a matching via rule.
+To place a via while routing, press :kbd:`v`. The "Layer pairs" rule defines which layer the router switches to. To change the size of vias, define a matching via rule or via definitions.
 
 You can also place vias not connected to any track with the "Place via" tool.
 
+See :doc:`vias` for how to use blind or buried vias.
 
 Importing logos
 ---------------

index.rst

@@ -55,6 +55,7 @@ Take a look at the :doc:`top features <feature-overview>`, just :doc:`try it out
    :caption: Board Editor:
 
    imp-board
+   vias
    copy-layout-placement
    backannotation
    rules

vias.rst

@@ -0,0 +1,38 @@
+Vias
+====
+
+As of version 2.5, Horizon EDA supports blind and buried vias. A via 
+consists of a Padstack that has the type Via, a parameter set that 
+sets the Padstack's parameters such as via and hole diameter and a span 
+that defines whether the via goes all the way through the board or is a 
+blind/buried via. There are three ways to define these elements of via 
+that can be selected by the source property.
+
+Local
+-----
+
+In this mode, all elements (padstack, parameter set and span) of the 
+via are set on the via itself. The via isn't affected by any rules.
+
+Rules
+-----
+
+In this mode, the "Vias" rules are evaluated based on the via's net to 
+set its Padstack and parameter set. The span is set on the via 
+itself. This mode is recommended for through vias.
+
+Definition
+----------
+
+In this mode, all elements of the via are set as per the selected via 
+definition. Via definitions are managed by the "Via definitions" rule.
+
+This mode is recommended for boards that use a stackup that allows for 
+blind or buried vias.
+
+Misc. notes
+-----------
+
+The STEP export omits non-through vias. For the gerber export, you'll 
+need to manually assign filename suffixes for each drill span used on 
+the board.