This task is a meta-task for "JSON support". Details are in the linked tasks.
MySQL-5.7 has JSON support in the above sense
Facebook has a DocStore-patch implementing JSON support in the above sense, which is incompatible with MySQL-5.7 implementation
We have Dynamic columns that can be used as a backing store for the JSON data (when is done)
Pluggable data types (MDEV-4912) might help here
There's an SQL standard early draft related to JSON support in SQL