Samsung SM-A20S schematic section for the power (on/off) and volume keys, delivered as a 4.63 MB PDF. It maps the side button flex or contacts, their signal lines toward the PMIC and processor, and the pull-up and protection parts involved. Handy when a phone will not power up from the button, a volume key is stuck or unresponsive, or a key line is suspected of leaking to ground. Open with a standard PDF viewer and use a multimeter in diode mode to compare readings along the traced lines.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @phoneSchematics. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.