Hello Partha,
Many thanks for your answer; it does describe a QinQ configuration for transport, as this other post did show: https://forums.juniper.net/t5/Ethernet-Switching/Q-in-Q-QFX-5100/m-p/307779.
What we're trying to achieve here is different, as we want to have a l3-interface on the same switch that communicates over double dot1Q. Using your configurations, we would need two physical switches to do that, which is not what we're looking for.
Regards,