Add support for directoryName subjectAltName

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/tests/data_files/Makefile b/tests/data_files/Makefile
index 7cdbd24..ce4a257 100644
--- a/tests/data_files/Makefile
+++ b/tests/data_files/Makefile
@@ -337,6 +337,10 @@
 
 server5-tricky-ip-san.crt: server5.key
 	$(OPENSSL) req -x509 -new -subj "/C=UK/O=Mbed TLS/CN=Mbed TLS Tricky IP SAN" -set_serial 77 -config $(test_ca_config_file) -extensions tricky_ip_san -days 3650 -sha256 -key server5.key -out $@
+	
+server5-directoryname.crt: server5.key
+	$(OPENSSL) req -x509 -new -subj "/C=UK/O=Mbed TLS/CN=Mbed TLS directoryName SAN" -set_serial 77 -config $(test_ca_config_file) -extensions directory_name_san -days 3650 -sha256 -key server5.key -out $@
+
 all_final += server5-tricky-ip-san.crt
 
 rsa_single_san_uri.crt.der: rsa_single_san_uri.key