DECT PHY events callback context

Hi All,

I have a question regarding modem DECT phy API.

There is a function nrf_modem_dect_phy_event_handler_set(nrf_modem_dect_phy_event_handler_t handler).
I'd like to know more information about handler:

1. Is this function callback called inside ISR context or inside zephyr thread context? 
2. Are there any strict limitations for the time processing inside that event callback handler?

Thanks in advance!