Designing for Low Cost China Manufacturing
All depends what kind of quality you want.

I'm doing assembly in China for about 10 years.

The truth is China doesn't really have a silicon industry in the likes of the US or Japan so finding chip equivalent with equivalent performance is gonna be a hard time. 

You can take a look at lcsc.com that is a Chinese reseller that has some chinese brand components.

Also be expected not to trust the datasheets given.

You will find basic chips, knock-off chips, fake chips... but you will have to pay a very, very high cost in reliability.

Most of PCBA manufacturer in China does NOT order parts from China and use Digikey, Mouser, etc..., because they (and their clients) don't trust suppliers in China. (Ironic)

I personally would not go down that road, unless you are trying to do dirt cheap boards at 10 cents a piece. I used to use passive components like ceramic and resistor from China and even this I stopped because I had often the case where it was the wrong values and when you will find out you have to rework your 10'000 boards because of a faulty chip / wrong components you will regret the 1$ you saved by board.

If you need to go down in cost, you can review your design, your BOM, order components in large quantities directly from the manufacturer, this is usually more effective and less risky than saving a few cent over a knock-off component.