Can you or someone recommend tutorial programming esp8266 "natively"? Most of the tutorial I cam across uses a mix of arduino IDE, nodemcu or micropython. I want to interact with esp8266 and the on-board mcu directly using C. I feel like these tools abstract away a whole lot of fundamental concepts, rendering most projects out there hobby-ish.

But I have limited knowledge on embedded programming. Hope someone can shed some material programming esp8266 from scratch. Thank you!