Importing CSV into multiple tables using PostgreSQL

I have a very big CSV file with the following format:

TAG,TIME,VALUE

as an example row:

footag,2014-06-25 08:00:00.0,3400.0

I used to import it easily inside PostgreSQL 9.3 using the following: COPY datapoints FROM '/home/foo/my.csv' DELIMITER ',' CSV; where datapoints is a table with the three corresponding columns.

Now, the database into which I need to import has changed. It has two tables. Here are \d+ outputs:

                                          Table "public.tags"
 Column |       Type        |                     Modifiers                     | Storage  | Stats target | Description
--------+-------------------+---------------------------------------------------+----------+--------------+-------------
 id     | integer           | not null default nextval('tags_id_seq'::regclass) | plain    |              |
 tag    | character varying | not null                                          | extended |              |
Indexes:
    "tags_pkey" PRIMARY KEY, btree (id)
    "tags_tag_idx" btree (tag)
Referenced by:
    TABLE "tag_values" CONSTRAINT "tag_values_tag_fkey" FOREIGN KEY (tag_id) REFERENCES tags(id)
Has OIDs: no

                                Table "public.tag_values"
 Column |            Type             | Modifiers | Storage | Stats target | Description
--------+-----------------------------+-----------+---------+--------------+-------------
 tag_id | integer                     | not null  | plain   |              |
 time   | timestamp without time zone | not null  | plain   |              |
 value  | double precision            |           | plain   |              |
Indexes:
    "tag_values_tag_time_idx" btree (tag_id, "time")
Foreign-key constraints:
    "tag_values_tag_fkey" FOREIGN KEY (tag_id) REFERENCES tags(id)
Has OIDs: no

So essentially, the original table is split into two. As you see, there's a foreign key constraint now (between tags(id) and tag_valued(tag_id)) Also, tags(tag) are supposed to be distinct. What is the easiest way to ingest the same .CSV files into such structure?

Thanks!