Just made two absrtactions, [serial_parseInt] and [serial_println], that work with Arduino's corresponding functions.
Did this mostly cause most of the Arduino code one can find, uses Serial.println(), when it comes to serial communication.

Get the abstractions with their help patches, and a simple Arduino code that works with the help patches here https://github.com/alexandros301/Arduino_println_parseInt_to_from_Pd

Update:
I made the [serial_println2] abstraction that can handle strings as key to values (one word strings only). The same git, goes with println2.ino Arduino sketch also provided from git.

Example:
you can write the following to the Arduino:
Serial.print("first");
Serial.println(value);

and diffuse the value in Pd with [route]. Check help patch for info.
Note: this one uses [bytes2any] from moocow.

Update:
I made the [serial_print] abstraction which can take in value printed with Serial.print() and separated by commas or spaces. Check its help patch for info (Arduino sketch provided).

Update:
I've changed the whole approach a bit. Now, there are three abstractions, [serial_print], [serial_println] and [serial_parseInt] (the first two have two versions each, a vanilla and an extended one, the extended version have the word extended in their name e.g. [serial_print_extendedd]).
Both [serial_print] and [serial_println] can handle strings, with the difference that the former can use a string as a tag for many numeric values, whereas the latter uses a string as a tag for a single numeric value.
Check help patches and Arduino sketches for info. GitHub page is the same.