Nested donut chart
Nested donut chart (also known as Multi-level doughnut chart, Multi-series doughnut chart) allows you to display multiple series in a single visualization. The series are usually related but represent different categories or slices of data (like the distribution of some category values over different years, etc.)
Support for multiple series
You can add any number of pie series to the pie chart. The chart will automatically nest them dividing available radius between each series, creating nested donuts.
More about nested donut charts
Demo source