How do I insert old partion into a table?

I like to insert old partion into a table. For example, partition (P201505) which contains May data needs to be inserted into tmp_table1. But the table already has partitions P201506 and P201507. The script for P201505 is following,

alter table tmp_table1 add PARTITION P201505 VALUES LESS  (201506) COMPRESS;

For partitions P201506 and P201507 are following. By the way, these partitions already exist on the table.

alter table tmp_table1 add PARTITION P201506 VALUES LESS  (201507) COMPRESS;
alter table tmp_table1 add PARTITION P201507 VALUES LESS  (201508) COMPRESS;

Please advise how to insert a old partition P201505 into a table considering that partitions P201506 and P201507 already exist on the table.