diff --git a/.gitmodules b/.gitmodules
index b9c9a33..3f4cfbd 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,6 +1,11 @@
-[submodule "source/prjxray"]
-	path = source/prjxray
-	url = ../prjxray
 [submodule "source/prjtrellis"]
 	path = source/prjtrellis
 	url = ../prjtrellis
+        branch = master
+[submodule "source/symbiflow-arch-defs"]
+	path = source/symbiflow-arch-defs
+	url = ../symbiflow-arch-defs
+        branch = master
+[submodule "source/prjxray"]
+	path = source/prjxray
+	url = ../prjxray
diff --git a/source/index.rst b/source/index.rst
index 163155f..e275153 100644
--- a/source/index.rst
+++ b/source/index.rst
@@ -7,5 +7,6 @@ SymbiFlow documentation
 
    introduction
    fasm-specification
+   symbiflow-arch-defs/docs/index
    prjxray/docs/index
    prjtrellis/docs/index
diff --git a/source/prjxray b/source/prjxray
index 78c47ab..91318ac 160000
--- a/source/prjxray
+++ b/source/prjxray
@@ -1 +1 @@
-Subproject commit 78c47ab82b65ebd1878437a418f595ee14415076
+Subproject commit 91318ac8a5928d0d692d61033932375736d03d43
diff --git a/source/symbiflow-arch-defs b/source/symbiflow-arch-defs
new file mode 160000
index 0000000..9c494d1
--- /dev/null
+++ b/source/symbiflow-arch-defs
@@ -0,0 +1 @@
+Subproject commit 9c494d1f43f87330d7eb3a7e6063f39b0933722b