Internal clamping circuit at the input pins of an MCU
simulate this circuit &ndash; Schematic created using CircuitLab

When Uin > 5.7V, the upper diode becomes conducting, and current flows from the input into the Vdd rail. Given the input current is supplied through a resistor, that limits Uin to ~5.7V. Same for Uin &lt; -0.7V. The lower diode becomes conducting then and Uin is limited to ~-0.7V.

It's called clamping because the diodes makes the input pin cling to the supply rails.

The "basic clamping circuit" you describe has nothing to do with this. That one limits an AC input to ±0.7V by using antiparallel diodes.