Android Marshmallow was released more than 6 months ago. So its about time that at least the flagship smartphones and tablets receive Marshmallow update. Sony have gone ahead and are rolling out Android Marshmallow for Xperia Z2, Z3, Z3 Compact and Z2 Tablet in India.
Surprisingly, Xperia Z2 has also got the Marshmallow update, even though it was released more than 2 years ago!
This update includes all the Marshmallow features like Doze which seeks to reduce power consumption while the device is not in use, Now On Tap which scans the screen for any relevant links and details to provide contextual abilities, and granular App Permissions that allows the user to have more control over just what aspects of their device apps have access to.
Sony is rolling out this update in phases so not all the devices will receive it simultaneously. If you want to check it, go to Settings >> About Phone >> Check for Updates.