In order to teleport, you cannot have any of the strength upgrades in your equipment screen. Otherwise when Link grabs the bush, he will just pick it up.
This trick is easiest with a bombchu, but it can be done with bombs as well using a different setup.
As adult, the most commonly used setup for this currently is composed of using the hookshot to shorten the backflip to ensure perfect positioning easily. It can be seen below.
As child, a different setup is needed.
1. With ISG, and your sword sheathed, align with the vertical line on the fence
2. Backflip and in C up mode align the B Button as shown
3. Sidehop twice to get closer to the correct position and destroy some of the grass, ensuring that you leave the bushes to your right and the one closest to the wall in front of you (The chu will explode when it hits the one in front, and the superslide will be activated off grabbing the bush to your right)
4. Stand just within "Grab" range of the bush in front of you and pull out a bombchu
6. Hold about 50% of the way back on the control stick so that link is walking backwards
7. After walking a couple of steps backwards, press and hold R, followed very quickly by mashing A whilst always holding down slightly. Link will drop the bombchu and sideroll to the right
8. Once you have the superslide, release and repress Z Target so you can see the bushes - this prevents them from unloading
9. When you are at the top of the grave, release everything and you will be teleported above the bush you tried to grab. Turn 180 degrees and backflip onto the seam
The same set up is usable for Adult Link, except 1 distance bombchu hover is required before you backflip onto the seam depending on the method.
This method is commonly used when one has a strength upgrade or no bombchus.
It might be a little difficult because you won't be able to see the bomb, but with practice it's easy. It's recommended that you face the wall at an angle so that link is facing a bit more towards the back of the graveyard than being perfectly perpendicular to the wall. This way you should get on the ledge in 3-4 bombs rather than 5 if you are perpendicular to the wall.
Shadow Early can also be done using the Invincibility Glitch method of Hookshot Jump.
This is the original method, but it is rarely used because it is not as practical as the other methods and is usually slower.
If you don't have Din's Fire to light the torches don't worry!
When done right, Link will hang on the ceiling once you clip through the staircase's ceiling, letting you avoid the load trigger for the torch room. Since the Shadow Temple door isn't loaded in the main graveyard room, you can simply walk right into the dungeon.
If you are in the upper graveyard area from playing the Nocturne of Shadow, you can do a ledge clip and jumpslash in.
Although the timing is tight, it's possible to light all the torches and open up the door to the Shadow Temple using the Fire Arrows.