Call it The Serena Rule.

As to avoid any confusion, the USTA revealed Friday that when a chair umpire issues a code violation, it will show up on the scoreboard.

During last September’s infamous US Open final, umpire Carlos Ramos levied three code violations against Serena Williams during her meltdown against eventual champion Naomi Osaka.

In one of her excuses, Serena said she thought Ramos had rescinded the first code violation for receiving coaching. The first code violation stood as a warning. The second violation — after Williams smashed her racket into the court — counted as a deducted point.

The third code violation was levied for “verbal abuse’’ after Williams, during a second-set changeover, called Ramos “a liar’’, “a thief’’ and threatened he’d never referee match of hers again. That cost her a full game.

Williams’ threat on Ramos may have come true. Ramos, the USTA announced, will not govern a Williams match during the fortnight for this year’s US Open. Williams opens with Maria Sharapova in Round 1 on Monday.

Serena skipped the annual Media Day on Friday at Armstrong Stadium.

Osaka, in tears during the championship ceremony because of the fan booing, was back on a Flushing court Friday for the first time since that fateful night. She was asked about the USTA’s decisions regarding more transparency on code violations and the Ramos ban.

“I never really say that I don’t like an umpire so I never change that,’’ Osaka said. “If I don’t want someone to umpire my match, I just go with whoever is doing it. And then I was just told about the code violation rule like it’s showing up on the screen? If it happens, it happens.’’

USTA officials said Williams camp did not ask for Ramos to be barred from Serena’s Open matches.

The USTA has new on-court leadership. Brian Early has stepped down as the U.S. Open referee, replaced by Soeren Friemel. Early was on court on Sept. 8, attempting to resolve the Williams-Ramos dispute — as well as others in the past involving the volatile Serena at the Open.

“In the end, our goal is to assign the best chair umpire for the right match,’’ Friemel said Friday. “So in taking all those factors into consideration, the decision was made he would not do any of the Williams sisters’ matches. He’s considered still for all (other) high-profile matches. It’s not the first time we made decisions where it’s good for the tournament, good for the players, good for the umpires to not be on those matches.’’

Osaka declined to answer two questions on Serena, including one on the state of their relationship since the blowup. They are on opposite sides of the draw and can meet again in the final. Williams topped Osaka in Montreal earlier this month in their lone meeting since.

“Can I pass, if that’s possible?,’’ Osaka said from the stadium podium after which the 1,000 fans on hand cheered.

On CBS TV this week, Osaka admitted she’s “nervous’’ to talk to Serena.

“I don’t say hi to her or anything because … I get so nervous,” Osaka said. “She always seems like she’s doing something important, so I don’t want to interrupt. And then — I really want to talk to her about life and stuff and how she manages to do things on and off the court. But I don’t wanna be disrespectful to her and, like, try to talk to her. Like she’s my mentor while she’s still playing. So I’m kinda just chillin’ on that.”

Osaka said she will tune in to the ballyhooed Williams-Sharapova match.

“Of course I’m going to watch it,’’ Osaka said. “I think everyone in New York is going to watch it. I’m not that surprised that happened. Every grand slam there is always some sort of drama. Like first round – Oh my God.”

The 21-year-old Japanese-American has also indicated that tennis hasn’t been as fun this year as it was in 2018 because of the extra pressure. She comes in as No. 1 seed and defending champion.

After the Open, she captured the Australian in January before slumping. She sustained a knee injury in the last Open tuneup in Cincinnati, retiring one week ago in the quarterfinals.

“It definitely changed for me,’’ Osaka said. “I took a break sort of and relaxed my mind and realized you have to have fun doing what you love. I love tennis. Sometimes I feel like I don’t.’’

Osaka could face 15-year-old phenom Coco Gauff in the third round. Gauff got a wild card into the main draw. The Open bent the rules in giving her a wild card because she already had received her maximum limit of three this year under USTA/WTA bylaws.

“She’s American,’’ Osaka said. “She played so well in Wimbledon. Why wouldn’t she play here? This is such a good experience for her. She obviously deserves to play here.’’