does it readily work when connected the MIPI-CSI of the microcontroller
No, neither MIPI DSI or CSI are "plug-and-play"... there is an expectation that you know what display / camera is connected, and how to operate it. It may be possible to "probe" the device to identify it, but you then need to know how to handle it.
does it need drivers to make it work?
Yes
If it does require drivers, are they specific to the camera or do they come with the MCU?
The software is generally split into two parts (aka drivers)... one for the MIPI CSI interface / peripheral in the host, and one for the device at the other end of the link. This pattern is common for a lot of things (e.g: I2C, SPI, USB, etc...) - abstraction is used to present the host-specific interface to the partner driver in a generic way, meaning that a different MCU can be swapped in without a full re-write.
That said... if you're operating at a more "baremetal" level (rather than an OS like Zephyr, Linux, etc...), then you may find the two merge somewhat, and you don't make the concious differentiation between the two.
do I need to write decoding logic to extract the frames? Will this be different if it was FLIR Boson thermal camera with MIPI-CSI?
Quite probably - though there is often hardware support for pulling pixels out of the raw data provided. Beyond configuring both the peripheral and device correctly, you'll also need to handle whatever data is provided - cameras can have different pixel formats (e.g: RGB, YUV444, YUV422, YUV420, etc...), frame formats (e.g: pentile, planar, semi-planar, non-planar), color depths, and more... There can also be algorithms like gain control which either operate on the host (requiring dynamic configuration) or on the camera (potentially requiring you to periodically query the configuration if you're after a somewhat calibrated output, like a thermal camera).
It's a complex area, and certainly not "plug and play"...!
