Merge pull request 0xPolygon#529 from 0xPolygon/zkevm/sc-class-diagram

zkEVM: class diagrams of Solidity files

Author: kmurphypolygon

docs/img/cdk/high-level-architecture/bridging-class-diagram.png

@@ -1,3 +1,5 @@
+![Polygon Solidity smart contract bridging architecture](../../../../img/cdk/high-level-architecture/bridging-class-diagram.png)
+
 The unified bridge transfers assets and messages between networks (L1, L2) by calling bridge and claim functions on the [PolygonZkEVMBridgeV2.sol](https://github.com/0xPolygonHermez/zkevm-contracts/blob/main/contracts/v2/PolygonZkEVMBridgeV2.sol) contract whose deployment address is an [upgradeable proxy](https://etherscan.io/address/0x2a3DD3EB832aF982ec71669E178424b10Dca2EDe#code). Interaction with the actual contract happens via the proxy.
 
 This contract is deployed on L1 and there is also one deployed on every L2 network. It communicates closely with an exit root manager contract specific to L1 or L2.

docs/img/cdk/high-level-architecture/exit-root-class-diagram.png

@@ -1,3 +1,7 @@
+The class diagram below describes how the exit root contracts communicate with the bridge and the rollup manager.
+
+![Polygon Solidity smart contract bridging architecture](../../../../img/cdk/high-level-architecture/exit-root-class-diagram.png)
+
 An exit tree is a binary, append-only, sparse Merkle tree (SMT) whose leaf nodes store bridging data. The exit trees have a depth of 32.
 
 The Merkle root of an exit tree is known as the exit tree root, and it is the fingerprint of all the information recorded in the exit tree's leaf nodes. 

docs/img/cdk/high-level-architecture/smart-contracts-full-view.png

@@ -2,13 +2,11 @@
 comments: true
 ---
 
-<!-- https://excalidraw.com/#json=JKZp9QEihifF_B7Z41Dfv,FVNhqQKi9PA1jM0kzUoCsQ" -->
-
 ## Polygon smart contract architecture
 
 Chain stacks at the node level direct transaction data to the L2 and L1 networks via smart contract calls. The system stores state in binary tree structures containing verifiable local and global exit roots.
 
-The diagram below details the Polygon Solidity smart contract architecture. 
+The diagram below details the Polygon Solidity smart contract architecture minus the bridging contracts. 
 
 ![Polygon Solidity smart contract architecture](../../../../img/cdk/high-level-architecture/smart-contracts-full-view.png)
 
@@ -39,6 +37,10 @@ The [PolygonRollupManager.sol](https://github.com/0xPolygonHermez/zkevm-contract
 
 ## Bridge 
 
+The class diagram below describes the unified bridge interactions.
+
+![Polygon Solidity smart contract bridging architecture](../../../../img/cdk/high-level-architecture/bridging-class-diagram.png)
+
 The unified bridge contract [PolygonZkEVMBridgeV2.sol](https://github.com/0xPolygonHermez/zkevm-contracts/blob/main/contracts/v2/PolygonZkEVMBridgeV2.sol) is responsible for bridging and claiming activity across L1 and L2 chains. 
 
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@@ -49,6 +51,10 @@ In the L1 network, the bridge also manages the complex exit root mechanism gover
 
 ## Global exit roots
 
+The class diagram below describes the exit root interactions.
+
+![Polygon Solidity smart contract bridging architecture](../../../../img/cdk/high-level-architecture/exit-root-class-diagram.png)
+
 System state as a whole is stored on binary trees with data and/or exit roots written into their leaves. 
 
 Local updates at the leaf-level trigger exit root updates at the top of the trees which are then available to the global exit root trees and the consensus contracts via the L1 bridge contract.