Does nxp provide any gdb serial support (for baremetal application) ?
What do you mean by 'Serial Support'? Are you running a debug monitor on the target?
Pretty much all debug is done via SWD (built-in debug connection) on Cortex-M parts, or JTAG (old, ARM7 or 9 based parts). The MCUXpresso is NXP's free toolchain (includes GDB and GCC, wrapped in an Eclipse IDE, but you can use them standalone if necessary). If using a SWD/JTAG, you need a debug probe such as LPC-Link2 (about $25), U-Link (Keil), J-Link (Segger) and Mulitlink (PEMicro).
I mean that I don't have swd or jtag, only serial.
I know there is something called gdb stub via serial.
But it requires driver/sw support.
For 'serial' debug, you need a debug monitor running on the target and AFAIK, there is no such thing for any modern ARM-ased MCU's (i.e NXP, ST, etc), So, no, there is no such thing. If you want to debug you *need* SWD.
For information on how to add SWD, see
Design Considerations for Debug
If this doesn't answer your question, please explain exactly what you have (chip, board ec) and exactly what you are trying to do, and why.
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