This auction is a tough one by any standard. If you play this as a game force you need 3 for the invitational raise, losing the option of supporting diamonds directly with some hands. This convention is a trick that can be used if you play this sequence as invitational only.
Responses with a weak notrump
2: Unbalanced 5+, possibly min.
2: 3-suiter with short, GF raise in or natural reverse (14+).
2: Natural reverse (14+)
2NT: Forcing and balanced
3: Not forcing with 3+.
3: GF, good 6+
3NT: 3-suited maximum.
1 - 2 - 2 - 2 (relay) - ?
2NT: 3-suited , minimum
3: GF, fit
3: 6+ + 4
3NT: 3-suited, medium
Other responses to the 2 bid.
2NT: 5332, minimum
3: Long and not much else.
Changes with a medium NT (13 - 15 / 14 - 16)
The direct 2NT rebid now shows (11)12 - 13 balanced, and 3NT shows a maximum, balanced or 3-suited (1-2 )
Changes with 15 - 17 NT and 1 not 18+ balanced
Since you need to cope with balanced hands that accept a game invitation more changes are needed. I suggest:
2NT directly: 12 - 13 balanced
3NT directly: 13+ - 14 balanced
2NT via the relay: Minimum 4441
3NT via the relay: Maximum 4441
If you need to include big balanced hands also it becomes a mess, so don't.