Update tx spec doc

docs/spec/transactions/README.md

@@ -6,15 +6,30 @@ and subject to change.
 ## Routing
 
 Ethermint needs to parse and handle transactions routed for both the EVM and for
-the Cosmos hub. We attempt to achieve this by mimicking [Geth's](https://github.com/ethereum/go-ethereum) `Transaction` structure to handle
+the Cosmos hub. We attempt to achieve this by mimicking [Geth's](https://github.com/ethereum/go-ethereum) `Transaction` structure and utilizing
-Ethereum transactions and utilizing the SDK's `auth.StdTx` for Cosmos
+the `Payload` as the potential encoding of a Cosmos-routed transaction. What
-transactions. Both of these structures are registered with an [Amino](https://github.com/tendermint/go-amino) codec, so the `TxDecoder` that in invoked
+designates this encoding, and ultimately routing, is the `Recipient` address --
-during the `BaseApp#runTx`, will be able to decode raw transaction bytes into the
+if this address matches some global unique predefined and configured address,
-appropriate transaction type which will then be passed onto handlers downstream.
+we regard it as a transaction meant for Cosmos, otherwise, the transaction is a
+pure Ethereum transaction and will be executed in the EVM.
+
+For Cosmos routed transactions, the `Transaction.Payload` will contain an [Amino](https://github.com/tendermint/go-amino) encoded embedded transaction that must
+implement the `sdk.Tx` interface. Note, the embedding (outer) `Transaction` is
+still RLP encoded in order to preserve compatibility with existing tooling. In
+addition, at launch, Ethermint will only support the `auth.StdTx` embedded Cosmos
+transaction type.
+
+Being that Ethermint implements the Tendermint ABCI application interface, as
+transactions are consumed, they are passed through a series of handlers. Once such
+handler, `runTx`, is responsible for invoking the `TxDecoder` which performs the
+business logic of properly deserializing raw transaction bytes into either an
+Ethereum transaction or a Cosmos transaction.
 
 __Note__: Our goal is to utilize Geth as a library, at least as much as possible,
 so it should be expected that these types and the operations you may perform on
 them will keep in line with Ethereum (e.g. signature algorithms and gas/fees).
+In addition, we aim to have existing tooling and frameworks in the Ethereum
+ecosystem have 100% compatibility with creating transactions in Ethermint.
 
 ## Transactions & Messages
 
@@ -33,16 +48,16 @@ no distinction between transactions and messages.
 Ethermint supports [EIP-155](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-155.md)
 signatures. A `Transaction` is expected to have a single signature for Ethereum
 routed transactions. However, just as in Cosmos, Ethermint will support multiple
-signers for `auth.StdTx` Cosmos routed transactions. Signatures over the
+signers for embedded Cosmos routed transactions. Signatures over the
-`Transaction` type are identical to Ethereum. However, the `auth.StdTx` contains
+`Transaction` type are identical to Ethereum. However, the embedded transaction contains
 a canonical signature structure that contains the signature itself and other
 information such as an account's sequence number. This, in addition to the chainID,
 helps prevent "replay attacks", where the same message could be executed over and
 over again.
 
-An `auth.StdTx` list of signatures must much the unique list of addresses returned
+An embedded transaction's list of signatures must much the unique list of addresses
-by each message's `GetSigners` call. In addition, the address of first signer of
+returned by each message's `GetSigners` call. In addition, the address of first
-the `auth.StdTx` is responsible for paying the fees.
+signer of the embedded transaction is responsible for paying the fees.
 
 ## Gas & Fees