diff --git a/clang/docs/MatrixTypes.rst b/clang/docs/MatrixTypes.rst
--- a/clang/docs/MatrixTypes.rst
+++ b/clang/docs/MatrixTypes.rst
@@ -266,6 +266,20 @@
   }
 
 
+Initialization Syntax
+---------------------
+A value of a matrix type M can be initialized with an initializer list:
+
+.. code-block:: c++
+
+  constexpr M m1 = {};
+  constexpr M m2 = {{a, b, c}, {d, e, f}};
+
+If the initializer list is empty, all elements of the matrix are zero-initialized. Otherwise, the initializer list
+must consist of M::rows initializer lists, each of which must consist of M::columns expressions, each of which is used
+to initialize the corresponding element of the matrix. For example, m[i][j] is initialized by the jth expression of the
+ith initializer list in the initializer. Element designators are not allowed.
+
 TODOs
 -----
 
@@ -274,9 +288,6 @@
 convenient. The alternative is using template deduction to extract this
 information. Also add spelling for C.
 
-Future Work: Initialization syntax.
-
-
 Decisions for the Implementation in Clang
 =========================================