What's actually here

Everything that knows about the chip lives in board/, so a program stays readable as just the program. Write yours in src/main.c, include esp32s3.h (the umbrella) plus whatever peripheral drivers you need on top — led.h for the onboard RGB LED — and never touch a register directly.

File	Job
`src/main.c`	Your program. A skeleton: boot the chip, then stop
`examples/`	One runnable program per peripheral — see its own README
`include/`	The headers: the whole API surface
`board/esp32s3.c`	`board_init()` — zero .bss, disable watchdogs, raise the clock
`board/esp32s3_clock.c`	CPU clock: read it, switch to 160 MHz, ungate peripherals
`board/esp32s3_console.c`	Text over USB-Serial-JTAG
`board/esp32s3_delay.c`	Busy-wait timing
`board/esp32s3_gpio.c`	Digital pins, and the GPIO matrix peripherals reach them through
`board/esp32s3_uart.c`	Hardware serial ports
`board/esp32s3_i2c.c`	I2C master
`board/esp32s3_spi.c`	SPI master on GP-SPI2
`board/esp32s3_pwm.c`	PWM on the LEDC peripheral
`board/esp32s3_watchdog.c`	Disable the ROM's watchdogs
`board/led.c`	Addressable RGB LED (WS2812) bit-banging driver
`board/esp32s3.ld`	Where the two segments land in SRAM
`Makefile`	Compile, link, convert to a flash image, flash it

src/main.c holds only board_init() and a halt. A program that does something is still just:

#include "esp32s3.h"
#include "led.h"

void _start(void)
{
    board_init();              /* .bss, watchdogs, 160 MHz */
    led_init(21);
    for (;;) {
        led_set_color(LED_RED);
        delay_ms(500);
        led_set_color(LED_OFF);
        delay_ms(500);
    }
}

Sizes, as text in the linked image:

Program	Size
`src/main.c` — boot and halt	352 B
the blink above	980 B
`examples/gpio_button.c`	1.4 KB
a program using all four buses	5.4 KB

Every driver is compiled every time, but --gc-sections drops each one the program never calls, so an unused bus costs nothing.