diff --git a/doc/src/arch/reference.rst b/doc/src/arch/reference.rst
index 5ae8e20b84b..0ed04d87694 100644
--- a/doc/src/arch/reference.rst
+++ b/doc/src/arch/reference.rst
@@ -114,6 +114,10 @@ Global FPGA Information
.. seealso:: :ref:`arch_grid_layout`
+.. arch:tag:: content
+
+ Content inside this tag specifies the layout of a single (2D) die; using multiple layer tags one can describe multi-die FPGAs (e.g. 3D stacked FPGAs).
+
.. arch:tag:: content
Content inside this tag specifies device information.
@@ -166,6 +170,37 @@ The valid tags within the ```` tag are:
Each ```` or ```` tag should contain a set of grid location tags.
+FPGA Layer Information
+----------------
+The layer tag is an optional tag to specify multi-die FPGAs. If not specified, a single-die FPGA with a single die (with index 0) is assumed.
+
+.. arch:tag::
+
+ :opt_param die:
+ Specifies the index of the die; index 0 is assumed to be at the bottom of a stack.
+
+ **Default**: ``0``
+
+ .. note:: If die number left unspecified, a single-die FPGA (die number = 0) is assumed.
+
+ .. code-block:: xml
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ .. note:: Note that all dice have the same width and height. Since we can always fill unused parts of a die with EMPTY blocks this does not restrict us to have the same usable area on each die.
+
Grid Location Priorities
~~~~~~~~~~~~~~~~~~~~~~~~
Each grid location specification has an associated numeric *priority*.