Otdfbt

Earlier in the season Jaime tells us:

Tormund: I'm no king. But if I were, I'd knight you 10 times over.

Jaime: You don't need a king. Any knight can make another knight.

_{Game of Thrones, Season 8 Episode 2, "A Knight of the Seven Kingdoms"}

He then proceeds to knight Brienne. In the final episode we learn that

Podrick

is now a knight and presumably Kingsguard, so who knighted him? There aren't many knights left in the main cast at least (Bronn, Brienne & Davos) so it must be one of them?

Is there any restrictions on when or how many times a knight can knight someone else?

There are three ways to become a knight in Game of Thrones.

Another knight can make you a knight:

Tormund: I'm no king. But if I were, I'd knight you 10 times over.

Jaime: You don't need a king. Any knight can make another knight.

_{Game of Thrones, Season 8 Episode 2, "A Knight of the Seven Kingdoms"}

As Podrick was Brienne's squire and served under her for quite a long time, it is very possible that she knighted him:

Podrick beams next to Jaime. Brienne paces. Bronn stands in the background.

Brienne: I don't need a squire.

Jaime: Of course you do.

_{Game of Thrones, Season 5 Episode 4, "Oathkeeper"}

A king can also make someone a knight, as King Joffrey Baratheon did to Ser Bronn because of his role in the Battle of Blackwater:

Podrick: Ser Bronn of the Blackwater was anointed by the king himself.

_{Game of Thrones, Season 3 Episode 1, "Valar Dohaeris"}

As Podrick appears to be a member of the Kingsguard, it seems possible that Bran could have anointed him for the position on the recommendation of Brienne and Tyrion.

Lastly, we know Lords and Ladies can knight someone, as Stannis did to Ser Davos for smuggling the onions into Storm's End under the siege. It's possible that as Podrick was Tyrion's squire for a while and Tyrion was quite fond of him he also could have knighted him.

I'd lean towards Brienne having done it, but lacking further evidence, we don't know for sure.

There's no explicit information regarding this but if we had to venture a guess, I'd say Brienne, presumably. Podrick squired for Brienne. And while it is not necessary, usually the Knight who one squires for knights him. We have examples both ways.

For example:

• Ser Duncan the Tall was knighted by his master Ser Arlan of Pennytree.


• Ser Loras Tyrell squired for Renly Baratheon and was knighted by him.


• Ser Barristan Selmy squired for Lord Manfred Swann but was knighted by King Aegon V for unhorsing the Crown Prince Duncan the Small, Prince of Dragonstone and his namesake the Lord Commander of the Kingsguard, Ser Duncan the Tall.


• Jaime Lannister squired for Lord Crakehall but he was knighted by Arthur Dayne.


• Aerys II Targaryen was knighted by Tywin Lannister even though he did not squire for him.


• Gregor Clegane was knighted by Rhaegar Targaryen, Prince of Dragonstone even though he did not squire for him.


• Raymun Fossoway, founder of Green-Apple Fossoways was knighted by
  Lord Lyonel Baratheon 'The Laughing Storm' even though he squired for
  his cousin, rather than Lord Baratheon.

Since Jaime Lannister knighted Brienne, she has the legal right to knight anyone she wants.

TORMUND: She's not a ser? You're not a knight?

BRIENNE: Women can't be knights.

TORMUND: Why not?

BRIENNE: Tradition.

TORMUND: Fuck tradition.

BRIENNE: I don't even want to be a knight.

TORMUND: I'm no king. But if I were, I'd knight you 10 times over.

JAIME: You don't need a king. Any knight can make another knight. I'll
prove it. Kneel, Lady Brienne. Do you want to be a knight or not?
Kneel. In the name of the Warrior, I charge you to be brave. In the
name of the Father, I charge you to be just. In the name of the
Mother, I charge you to defend the innocent. Arise, Brienne of Tarth a
knight of the Seven Kingdoms.

TYRION: Ser Brienne of Tarth! Knight of the Seven Kingdoms!
_{S08E02 - A knight of the Seven Kingdoms}

There is no restriction over who and how many a Knight can Knight. It's usually honour that stops the abuse. While some knights are known to sell knighthood in return for material benefits (See Ser Glendon Flowers of Pussywillows who bought his knighthood by selling his sister's maidenhead to Ser Morgan Dunstable), Knighthood is not all that simple. The honour and reputation of the Knight who's doing the knighting plays a huge role in the about-to-be knighted squire's life. If he was dishonourable, you'd be seen as such as well. If a Knight freely uses his privilege, his bestowed knighthood would be seen as a joke, rather than rightful culmination of a long and arduous process. He'll become notorious in the country and anyone would be foolish to ask him to knight them. Ser Perkin the Flea did so, luring cuthroats and scum of the King's Landing to support Trystane Truefyre, knighting every man who did so. He was eventually sent to the wall for regicide. His cutthroat 'Knights' scattered to four winds, none daring to claim Knighthood since then questions would be asked and they'd be identified as lowborn scum knighted by traitor Ser Perkin. As GRRM said (Credits: Mooz)

[Interviewer] Yet if every knight can create a knight as we have seen in "The Hedge Knight", what prevents a widespread misuse by unscrupulous hedge knights such as Ser Osmynd Kettleblack or the cynical Great Houses?

[GRRM] Social pressure. A knight's peers would look with a certain amount of disfavor on anyone who did this. They might gain money, but they would lose honor. And honor is still very important in this culture.

Also see:

• What are the benefits of Knighthood?


• Who can Knight you so that the knighting sticks?