landsat - Maximum ndvi for 3 months average in Google Earth Engine

I have a ndvi series which I am able to plot using below code:

var ndvi = l8.map(function(image) {
  return image.select().addBands(image.normalizedDifference(['B5', 'B4']));

});
var ndviChart = ui.Chart.image.series(ndvi, point, ee.Reducer.mean(), 500);
print(ndviChart);

My goal is to calculate the average ndvi for every 3 months window and then calculate the maximum ndvi over that 3 months window. How to access data in ui.Chart.series and is there any way by which I can do the above calculation on Google server ?

In javascript it can be done using

I want to replace lista with ndviChart series. Can anybody help me in this direction?