What are the advantages of using an audio codec with mainline Linux support?

I am a hardware designer who is working on a custom processor circuit board with audio support. Our intention is to have the processor running some flavor of Linux and interface with the audio chip over PDM/I2S. One of my considerations in selecting an audio chip is minimizing headaches for our software team. I would like to pick something that simplifies the driver development process, if possible. In my research, I came across this Texas Instruments Linux driver page that explains that they have a driver "available in the Linux mainline". My gut sense is that having mainline Linux support sounds like an advantage, but I don't understand it enough to explain what the advantage is, or have a sense of how much effort it will save. I also came across linux/sound/soc/codecs in the Linux kernel Github page. Is this the list of audio chips that are "available in the Linux mainline"? Can I pick any of the chips listed here and assume that it will make the software team's life easier? Will they be able to simply enable the driver in the kernel, and the OS will recognize the audio chip automatically? What exactly does it mean to have a driver in the Linux mainline? How do I know what chips have mainline drivers, and how much of an advantage is it to use them?