user: Add basic lpc24xx description

Update #3724.
Update #3725.

user/bsps/bsps-arm.rst

@@ -275,10 +275,79 @@ lpc176x
 
 TODO.
 
-lpc24xx
-=======
+lpc24xx (NXP LPC17XX/LPC24XX/LPC40XX)
+=====================================
 
-TODO.
+This BSP offers only several variants.  The following variants support the
+`Embedded Artits LPC4088 Developer's Kit <https://www.embeddedartists.com/products/lpc4088-developers-kit/>`_
+and earlier board generations:
+
+* lpc17xx_ea_ram
+
+* lpc17xx_ea_rom_int
+
+* lpc24xx_ea
+
+* lpc40xx_ea_ram
+
+* lpc40xx_ea_rom_int
+
+They can be used as a base line for customization.  The basic hardware
+initialization is performed by the BSP.  It can be customized via configuration
+options and configuration tables.  See also
+`<bsp/start-config.h> <https://git.rtems.org/rtems/tree/bsps/arm/lpc24xx/include/bsp/start-config.h>`_.
+
+Clock Driver
+------------
+
+The clock driver of the Cortex-M variants uses the `ARMv7-M Systick`.  The
+older ARM7TDMI variants use the `TMR0` timer module.
+
+Console Driver
+--------------
+
+The console driver supports up to four on-chip UARTs.  Initialization can be
+customized via the ``lpc24xx_uart_probe_1()``, ``lpc24xx_uart_probe_2()`` and
+``lpc24xx_uart_probe_3()`` functions.
+
+I2C Bus Driver
+--------------
+
+I2C bus drivers are registered by the ``lpc24xx_register_i2c_0()``,
+``lpc24xx_register_i2c_1()`` and ``lpc24xx_register_i2c_2()`` functions.  The
+I2C driver does not configure the pins.  See also
+`<bsp/i2c.h> <https://git.rtems.org/rtems/tree/bsps/arm/lpc24xx/include/bsp/i2c.h>`_.
+
+SPI Bus Driver
+--------------
+
+SPI bus drivers are registered by the ``lpc24xx_register_ssp_0()``,
+``lpc24xx_register_ssp_1()`` and ``lpc24xx_register_ssp_2()`` functions.  The
+SSP driver does not configure the pins.  See also
+`<bsp/ssp.h> <https://git.rtems.org/rtems/tree/bsps/arm/lpc24xx/include/bsp/ssp.h>`_.
+
+Network Interface Driver
+------------------------
+
+Only a legacy network driver is support.  For a `libbsd` base driver the
+platform support is missing, see
+`if_lpe.c <https://git.rtems.org/rtems-libbsd/tree/rtemsbsd/sys/arm/lpc/if_lpe.c>`_.
+
+USB Driver
+----------
+
+The USB host driver (OHCI) is provided by the `libbsd`.
+
+Framebuffer Driver
+------------------
+
+For a custom framebuffer driver see
+`<bsp/lcd.h> <https://git.rtems.org/rtems/tree/bsps/arm/lpc24xx/include/bsp/lcd.h>`_.
+
+RTC Driver
+----------
+
+There is a standard RTC driver available using the on-chip RTC module.
 
 lpc32xx
 =======