Add Changelog entry for the new ECDH context
diff --git a/ChangeLog b/ChangeLog
index 8f0e8c1..f3dca40 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 mbed TLS ChangeLog (Sorted per branch, date)
 
+= mbed TLS 2.x.x branch released xxxx-xx-xx
+
+Changes
+   * Extend ECDH interface to enable alternative implementations.
+
 = mbed TLS 2.14.0 branch released 2018-11-19
 
 Security