[PATCH] eng: Document use of BSP family for defaults

[Sebastian Huber]

Update #4468.
---
 eng/build-system.rst | 4 ++--
 eng/req/items.rst    | 8 ++++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/eng/build-system.rst b/eng/build-system.rst
index e76b606..030679d 100644
--- a/eng/build-system.rst
+++ b/eng/build-system.rst
@@ -355,8 +355,8 @@ Add a Base BSP to a BSP Family
     items ``spec:/build/bsps/arch/family/bsprst``,
     ``spec:/build/bsps/arch/family/bspuvw``, and
     ``spec:/build/bsps/arch/family/bspxyz`` just define the name of the base
-    BSP and set a link to the group item.  The base BSP names can be used for
-    example in the ``default-by-variant`` attribute of
+    BSP and set a link to the group item.  The base BSP and BSP family names
+    can be used for example in the ``default-by-variant`` attribute of
     :ref:`SpecTypeBuildOptionItemType` items.  The items linked by the BSP
     items are shown using relative UIDs.
 
diff --git a/eng/req/items.rst b/eng/req/items.rst
index e7727aa..51f3c3d 100644
--- a/eng/req/items.rst
+++ b/eng/req/items.rst
@@ -719,8 +719,11 @@ default
 
 default-by-variant
     The attribute value shall be a list. Each list element shall be a
-    :ref:`SpecTypeBuildOptionDefaultByVariant`. The list is processed from top
-    to bottom.  If a matching variant is found, then the processing stops.
+    :ref:`SpecTypeBuildOptionDefaultByVariant`. The list is checked two times
+    and processed from top to bottom. Firstly, the base BSP name is used to
+    match with a variant. Secondly, the BSP family name prefixed by ``bsps/``
+    is used to match with a variant.  If a matching variant is found, then the
+    processing stops.
 
 description
     The attribute value shall be an optional string. It shall be the
@@ -750,6 +753,7 @@ Please have a look at the following example:
     default-by-variant:
     - value: 9600
       variants:
+      - bsps/powerpc/motorola_powerpc
       - m68k/m5484FireEngine
       - powerpc/hsc_cm01
     - value: 19200
-- 
2.26.2