While triple- or even quad-charging an engine isn't an unheard of concept, it's not so common for automakers to embrace such overly complicated technology. Volvo did it a few years back with a twin-turbo two-litre that used an additional electric turbo for quicker spool, but it has yet to go into full swing production (and probably never will).
But Mazda seems to be interested in the concept after a patent (1) / (2) was filed last week that contains schematics for a four-cylinder engine that is equipped with two turbos and an electric supercharger. Patents are pretty wordy documents, so after a quick skim read it seems that it will look to achieve a similar effect to the Volvo design where the supercharger builds boost from the get go to reduce lag.
What's getting most people excited is the fact that those schematics show it running in a rear-wheel drive configuration, and there are rumours spreading around that it could be the successor engine to the fabled RX family ...
Deeper reading reveals mentions of the potential as a diesel engine, and there's an oddly designed piece on the bottom which may hint at four-wheel drive capabilities. We don't really know and nothing official has been announced by Mazda as of yet.
We eagerly await to find out what the automaker has up it's sleeve.