KiCad boards from 2 GitHub repositories tagged “at89s52”, the most starred first; open any of them in PCBKit.
21shravan/AT89s51-dev-board
A modern AT89S52 (8051) development board featuring USB Type-C power, CH340C USB-to-UART, ISP programming, and a complete open-source hardware design documented from schematic to PCB.
HeyPCB/hello-8051
HELLO: a tiny 8051 computer shaped like a 1984 desktop. AT89S52, 32 KB SRAM, 128x64 ST7920 LCD, USB-C. 112 x 158 mm 2-layer KiCad 10 board, DRC clean, firmware that writes hello. Built through HeyPCB's MCP server.