Merge pull request #789 from ethereum-optimism/bm/bridging-via-eth-transfer

doc: bridging via simple ETH transfer.

Author: cpengilly

pages/builders/app-developers/bridging/standard-bridge.mdx

@@ -191,6 +191,12 @@ The Standard Bridge contracts can also be used to bridge ETH from Ethereum to OP
 The ETH bridging process is generally less complex than the ERC-20 bridging process.
 Users simply need to trigger and send ETH to the [`bridgeETH`](https://github.com/ethereum-optimism/optimism/blob/2e647210882d961f04055e656590d90ad98c9934/packages/contracts-bedrock/src/universal/StandardBridge.sol#L143-L150) or [`bridgeETHTo`](https://github.com/ethereum-optimism/optimism/blob/2e647210882d961f04055e656590d90ad98c9934/packages/contracts-bedrock/src/universal/StandardBridge.sol#L152-L166) functions on either blockchain.
 
+  <Callout>
+    Users can also deposit ETH from Ethereum to OP Mainnet by sending a basic ETH transfer from an EOA to the `L1StandardBridgeProxy`. 
+    This works because the `L1StandardBridgeProxy` contains a [`receive`](https://github.com/ethereum-optimism/optimism/blob/2e647210882d961f04055e656590d90ad98c9934/packages/contracts-bedrock/src/universal/StandardBridge.sol#L119-L121) function.
+    You can find the mainnet and testnet addresses on the [Contract Addresses](/chain/addresses) page.
+  </Callout>
+
 ## Tutorials
 
 *   [Learn how to bridge ERC-20 tokens with the Optimism SDK](/builders/app-developers/tutorials/cross-dom-bridge-erc20)