Mahindra Ecole Centrale

His JEE Mains marks are very less but he can try.
If seats are available, he might get admission.

You might have a chance if you have any reservation criteria else give it a try. You have very great chance to get into this institute with this rank. Attend the counselling and choose your options appropriately. Try Shiksha college predictor for better analysis.

https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor
Please, go to the college predictor link I am sharing here to know about the college you can get. Good luck.

TS EAMCET 2018 College Predictor
Use your TS EAMCET 2018 rank to see where you can get admission at the link provided below:
See the courses, colleges & rounds you may crack
The result is based on admissions data of TS EAMCET 2017
Get resources & insights on colleges & courses
https://www.shiksha.com/b-tech/resources/ts-eamcet-college-predictor.

With 23000 rank, you can get a seat moreover in some newer NITs or your home state NIT. You may or may not get CSE ECE IT but you can get other branches for sure. Why to give donation when you are having a decent rank. You can try for LNMIIT, IIIT ( international one's) which gives admission solely on the basis of marks and no rank. And regarding fees. LNMIIT is a bit costly which cost about 3 Lacs per year. IIIT may cost about 2 Lacs per year. Hope it helps.

Yes, your son can definitely get a seat in CSE on the basis of Intermediate score. It is too good.
Best of luck for your future and if there's any query, feel free to ask.

Please refer to the link provided below for a detailed fee structure for B.Tech in Mechanical Engineering from Mahindra Ecole Centrale College of Engineering:
https://www.shiksha.com/b-tech/course/b-tech-in-mechanical-engineering-mahindra-ecole-centrale-college-of-engineering-bahadurpally-hyderabad-230047

Follow the links below to verify:
Rank prediction : https://www.shiksha.com/b-tech/resources/jee-main-rank-predictor
College prediction : https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor