Add migration guide and changelog
Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
diff --git a/ChangeLog.d/split-config.txt b/ChangeLog.d/split-config.txt
new file mode 100644
index 0000000..bb807be
--- /dev/null
+++ b/ChangeLog.d/split-config.txt
@@ -0,0 +1,12 @@
+Changes
+ * config.h has been split into build_info.h and mbedtls_config.h
+ build_info.h is intended to be included from C code directly, while
+ mbedtls_config.h is intended to be edited by end users whishing to
+ change the build configuration, and should generally only be included from
+ build_info.h.
+ * The handling of MBEDTLS_CONFIG_FILE has been moved into build_info.h.
+ * Mandatory version symbols MBEDTLS_CONFIG_VERSION and
+ MBEDTLS_USER_CONFIG_VERSION were introduced for MBEDTLS_CONFIG_FILE and
+ MBEDTLS_USER_CONFIG_FILE respectively. They have to be defined with a
+ value of one in their respective config file for the config to be
+ considered valid.