[test]: add README.md for mpi unit test

Change-Id: Ia540cd26cf33f3205cbf3629b3fc2ac3a080cc7d
Signed-off-by: sliver.chen <sliver.chen@rock-chips.com>

test/README.md

@@ -0,0 +1,29 @@
+# Unit test description
+
+## There are some unit test for testing mpp functions in this catalog.
+
+### mpi_enc_test:
+use sync interface(poll,dequeue and enqueue), encode raw yuv to compress video.
+
+### mpi_dec_test:
+use sync interface and async interface(decode_put_packet and decode_get_frame),
+decode compress video to raw yuv.
+
+### mpi_rc_test:
+encode use detailed bitrate control config.
+
+### mpi_rc2_test:
+encode use detailed bitrate control config,and cfg param come from mpi_rc.cfg.
+
+### mpi_test:
+simple description of mpi calling method, just for reference
+
+### mpp_event_trigger:
+event trigger test.
+
+### mpp_parse_cfg:
+mpp parser cfg test.
+
+### vpu_api_test
+encode or decode use legacy interface, in order to compatible with the previous
+vpu interface.