README: Enable builds as a CMake subproject
Update the README with information on a newly supported feature: the
ability to build Mbed TLS as a subproject of another CMake project.
diff --git a/README.md b/README.md
index 5b01603..be26f56 100644
--- a/README.md
+++ b/README.md
@@ -146,6 +146,12 @@
your value of CFLAGS doesn't override the content provided by cmake (depending
on the build mode as seen above), it's merely prepended to it.
+#### Mbed TLS as a subproject
+
+Mbed TLS, like Mbed Crypto, supports being built as a CMake subproject. One can
+use `add_subdirectory()` from a parent CMake project to include Mbed TLS as a
+subproject.
+
### Microsoft Visual Studio
The build files for Microsoft Visual Studio are generated for Visual Studio 2010.