Add third_party/dtc submodule

Change-Id: I8192fcc56304abf45ffd0df906127fe71a4c0b9f
diff --git a/.gitmodules b/.gitmodules
index 13fb56f..ef9e75a 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -6,6 +6,10 @@
 	path = project/reference
 	url = https://hafnium.googlesource.com/hafnium/project/reference
 	shallow = true
+[submodule "third_party/dtc"]
+	path = third_party/dtc
+	url = https://hafnium.googlesource.com/hafnium/third_party/dtc
+	shallow = true
 [submodule "third_party/googletest"]
 	path = third_party/googletest
 	url = https://hafnium.googlesource.com/hafnium/third_party/googletest
diff --git a/third_party/dtc b/third_party/dtc
new file mode 160000
index 0000000..f4d9058
--- /dev/null
+++ b/third_party/dtc
@@ -0,0 +1 @@
+Subproject commit f4d9058c550b8b85c760bd53c1f358671b635d5e